thought experiments in science fiction

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The Forever War: understanding, science fiction, and thought experiments

Harald a. wiltsche.

Department for Culture and Communication, Linköping University, 581 83 Linköping, Sweden

The aim of this paper is to show that scientific thought experiments and works of science fiction are highly suitable tools for facilitating and increasing understanding of science. After comparing one of Einstein’s most famous thought experiments with the science fiction novel “The Forever War”, I shall argue that both proceed similarly in making some of the more outlandish consequences of special relativity theory intelligible. However, as I will also point out, understanding in thought experiments and understanding in science fiction differ in one important respect: While the former aim at what I shall call “physical understanding”, science fiction novels typically have “existential understanding” as their target.

Introduction

Looking back at the past three decades, the philosophical debate about thought experiments (“TEs”) is characterized by a strong focus on their alleged knowledge-producing powers (cf., for an overview, Brown and Fehige 2017 ). This might seem surprising, especially in light of the historical record. Although it is certainly correct that some TEs were intended to facilitate knowledge about reality, more often than not TEs in science seem to have served other purposes, such as disclosing inconsistencies in existing theories or, perhaps even more important, making consequences of theories easier to understand. Given this, and given the strong focus on knowledge production in the existing literature in philosophy of science, it might be worth paying closer attention to how understanding of theories and/or the phenomena in their domain is facilitated through TEs.

As has been recently noted (Stuart 2018 ), such a shift in attention gains additional plausibility from recent work in mainstream philosophy of science and epistemology. The epistemic value of understanding has been marginalized for the better part of the twentieth century. To some extent, this was due to the general fixation with propositional knowledge that characterizes much of Western philosophy. In philosophy of science, the neglect of understanding was further exacerbated by the assumption that understanding is merely a subjective byproduct of explanation, a feature that was taken to be describable in terms of objective relations between theory and evidence alone. 1 In recent years, however, the philosophical winds have shifted. Nowadays a growing number of philosophers argue that understanding is an epistemic good that needs to be studied in its own right or, even more forcefully, that understanding ought to supplant knowledge and explanation as the focus of philosophical attention (e.g. Kvanvig 2003 ). Though space does not permit me to enter this discussion here (cf., e.g., De Regt et al. 2005 ; De Regt 2017 ; Grimm et al. 2017 ), it should be apparent that the “recovery” of understanding in mainstream philosophy also has consequences for the discussion about scientific TEs: If understanding is not just a feeling, but one of the principal epistemic aims of science, and if, furthermore, TEs are particularly apt to increase understanding, then coming to terms with the reasons for this aptness is without doubt an important task (cf. also Stuart 2016 ).

There is yet another reason to look more closely at the ways in which TEs facilitate understanding. Recent years have seen increasing attention to TEs, but also to the relations between TEs and other areas of philosophical interest. For instance, following early suggestions by Davenport ( 1983 ) and Sorensen ( 1992 ), philosophers have started to explore the connections between TEs and works of literary fiction (cf., e.g., Carroll 2002 ; Davies 2007 ; Swirski 2007 ; Elgin 2007 , 2014 ; De Smedt and De Cruz 2015 ; Egan 2016 ). The presumption that such a comparison might be fruitful is indeed a natural one: Like TEs, works of literary fiction require their readers to cognitively participate in fictional narratives in which hypothetical or counterfactual scenarios are described. And like TEs, some works of literary fiction allow us to learn something about reality, even though they are usually written without “fidelity constraint” (Davies 2007 , p. 31), i.e. without the requirement to include only events that are believed to have occurred. However, in this discussion too, a strong emphasis on knowledge production does not seem to be the most natural starting point. Of course, there is a trivial sense in which we do acquire propositional knowledge about reality from works of literary fiction: Since it contains much factual information about life in the middle ages, a lot about medieval Italy can be learned from reading Eco’s The Name of the Rose . And whenever we have finished reading a work of fiction, we have thereby gained knowledge that we have just read a work of fiction. However, such trivialities aside, it strikes me as odd to say that the cognitive outcome of my reading of Nineteen Eighty-Four is an increase in my stock of true propositions about the physical world. Even if I did not learn anything new about the world, Orwell’s novel may help me to understand how the corruption of the media aids totalitarian regimes. 2

With these generalities in mind, let me say a word about the aim and the structure of my paper. In part one, I will try to get a grip on the kind of understanding that is brought about in scientific TEs. To this end, I shall discuss Einstein’s train, a TE that is commonly used to elucidate one of the more counter-intuitive consequences of special relativity theory (“SR”). In part two, I will give a brief summary of Joe Haldeman’s science fiction novel The Forever War (“TFW”). One of the intriguing aspects of TFW is that it depicts a fictional world in which technological innovations make the effects of SR directly experienceable. Based on the comparison between Einstein’s train and TFW, I shall argue that both proceed similarly in making fairly outlandish consequences of SR intelligible. However, as I will point out in the final part of my paper, understanding in TEs and understanding in science fiction nevertheless differs in one important respect: While TEs in physics aim at what I shall call physical understanding , science fiction novels like TFW have existential understanding as their target.

Einstein’s train

Science has a history of challenging deeply entrenched empirical intuitions about reality. Many intuitions that were thought to reflect substantial metaphysical insights turned out to be of limited reliability because they were formed under non-generalizable conditions. For instance, our experiences are usually limited to objects that are moving with velocities much lower than the speed of light. Although intuitions that are formed on this experiential basis may be adequate to account for most everyday phenomena, they fail to provide a conceptual basis for a scientific treatment of motion in general. The revolution in physics that occurred at the beginning of the twentieth century helps to make this point vivid.

Following Einstein’s canonical presentation, SR rests on two explicit postulates. The first, referred to as the principle of relativity , is known since the times of Galileo and states that the laws of physics are the same in every inertial frame of reference. The second postulate, referred to as the light principle , is a consequence of the first: If Maxwell’s equations hold in all inertial frames, then the only possible value of the speed of light in all inertial frames is c . Building on these two postulates, Einstein introduces a definition of simultaneity according to which two events, e 1 and e 2 , are simultaneous if and only if light flashes emitted from both events meet exactly at the spatial midpoint between e 1 and e 2 .

Taken in isolation, the two postulates and the definition may appear innocent enough: While the principle of relativity states that the outcome of any given experiment is independent from the inertial frame in which it is performed, the light principle states that the velocity of light is constant in all inertial frames, and independent from the velocity of the emitting source. And once the constancy of c is accepted, Einstein’s definition of simultaneity follows naturally. In conjunction, however, the two postulates yield several perplexing consequences: it follows, for instance, that the question whether two spatially distant events occur at the same time cannot be answered in an absolute, frame-independent sense. In the next paragraphs, I shall discuss two strategies to bring this consequence, which is usually referred to as the relativity of simultaneity , to the fore. While the first is to derive the relativity of simultaneity from the mathematical formalism of SR, the second relies on one of Einstein’s most celebrated TEs. A comparison between the two strategies will help to gain a clearer grasp of the kind of understanding that is brought about in TEs.

A crucial component of modern physical theories are the transformation rules that describe the relationship between the coordinates ( x ,  y ,  z ,  t ) and ( x ′ , y ′ , z ′ , t ′ ) of a set of events, as measured in two inertial frames S and S ′ that differ only in their constant relative motion, with velocity v . In pre-relativistic physics, the coordinates are related to one another by the Galilean transformations, which are given by the equations

The final equation t ′ = t codifies the pre-relativistic intuition that time is invariant under Galilean transformations and that, consequently, the temporal order of two events e 1 and e 2 always stays the same, no matter from which reference frame e 1 and e 2 are measured. Note, however, that the Galilean transformations are incompatible with the postulates of SR. If t ′ = t and x ′ = x - v t , then parallel velocities add and no velocity can be invariant across inertial frames that are in motion with respect to each other. This means that, contrary to the light principle, the value of c would change depending on the relative motion of the inertial frame from which c is measured. As a consequence, the Galilean transformations must be replaced by transformation rules that are compatible with the postulates of SR (and with the implicit assumption that space is homogenous and isotropic). These conditions are satisfied by the Lorentz transformations that are given by the equations

Upon applying the Lorentz transformations to relate the coordinates of e 1 and e 2 , one realizes that the question whether e 1 and e 2 occur simultaneously cannot be answered in an absolute, frame-independent way. Assume that e 1 and e 2 have identical values of the t -coordinate for an observer at rest. A little bit of algebra reveals that the same events e 1 and e 2 will have different values of the t ′ -coordinate if measured by an observer in uniform relative motion with respect to the first.

The point of the previous paragraph was to illustrate that one of the more counter-intuitive consequences of SR can be directly read off from its mathematical core. I shall say more on this approach in a moment. But let me first turn to the second strategy, that of demonstrating the relativity of simultaneity through a TE.

In one of his most celebrated TEs, Einstein ( 2005 , pp. 25–27) asks us to imagine a train that is traveling along a straight track with constant velocity v . Let e 1 and e 2 be two separate events that emit light flashes at opposite ends of the train. Suppose furthermore that an observer is standing next to the train tracks right at the spatial midpoint between e 1 and e 2 . Since both light flashes travel with the constant velocity c , both arrive at the observer’s position at the exact same time. The observer thus concludes that e 1 and e 2 must have happened simultaneously (cf. Fig.  1 ).

The situation for the second observer

But now imagine a second observer who experiences the same situation from within the train. Although the second observer is also initially located at the spatial midpoint between e 1 and e 2 , the light from e 1 arrives at her position a little bit later than the light from e 2 . It is easy to see why (cf. Fig.  2 ). Light from both sources requires time to reach the observer’s position. But during that time the train moves towards e 2 with velocity v , which means that light from e 1 has a longer distance to cover until it catches up with the moving observer. Hence, since the light signals from e 1 and e 2 arrive at her location at different times, the moving observer rightly judges that e 1 and e 2 did not happen simultaneously. Upon reflecting on how the same scenario plays out for two observers in different inertial frames, we thus arrive at the desired conclusion: The simultaneity of two distant events is relative to a frame.

Physics textbooks typically feature discussions of both strategies to demonstrate the relativity of simultaneity. It is interesting to see, however, that in virtually all cases the mathematical derivations are given after the basic idea has been introduced through a TE. The reason has to do with the differences between the kinds of understanding that are brought about by the two strategies outlined above. But before I can argue for this claim, some general remarks about the cognitive achievement of understanding are in order.

Broadly speaking, I subscribe to a “manipulationist” account according to which the crucial aspect of understanding is its empowering role : Unlike those lacking understanding, understanders are in a position to effectively use whatever it is they have understood. This intuition has been elaborated by a number of thinkers, for instance by Hasok Chang, who ties understanding to the performability of an “epistemic activity” (Chang 2009 ). Following Chang’s usage of the term, an epistemic activity is a “coherent set of mental or physical actions (or operations) that are intended to contribute to the production or improvement of knowledge in a particular way, in accordance with some discernible rules” (Chang 2011 , p. 209). On this view, then, a cognitive agent understands P (an object, a theory, a model, an equation, a concept, a technique, an instrument, etc.), if she has the skills to perform the epistemic activities that are relevant to P . Using the terminology employed by Hills ( 2016 ), the intuition underlying Chang’s proposal may also be expressed in terms of “cognitive control” or “cognitive grasp”: 3 To understand P not only means to be in possession of a set of true propositions pertaining to P . In order to understand P , a cognitive agent must also have the abilities to bring P under her cognitive control by engaging in relevant epistemic activities with respect to P , i.e. by manipulating P , by giving an explanation of why P or by applying the relevant abilities to P ′ , where P ′ is sufficiently similar to but not identical with P .

Perhaps the most sophisticated manipulationist account comes from Daniel Wilkenfeld. Building on a proposal by De Regt and Dieks ( 2005 ) and in line with Chang’s views on the matter, Wilkenfeld agrees that understanding ought to “be characterized largely in terms of what it enables one to do” (Wilkenfeld 2013 , p. 1000). However, for reasons which will become clear in a moment, Wilkenfeld goes beyond other existing accounts by introducing the additional condition that in order to understand P , a cognitive agent must also possess (or be able to construct) a mental representation of P . Of course, not every mental representation will do. According to Wilkenfeld, “a mental representation counts as being ‘of the right sort’ in virtue of the fact that possession of it enables one to perform (typically, but not always, intellectual) feats relevant in that context” (Wilkenfeld 2013 , p. 1000). Hence, on this view, a cognitive agent understands P if, first, she is able to construct a mental representation of P and if, second, she is able to perform the epistemic activities that are relevant to (the mental representation of) P . 4

On the view just described, demonstrating the relativity of simultaneity using the Lorentz transformations certainly counts as an epistemic activity in Chang’s sense of the term. In order to obtain the desired result, a cognitive agent must perform certain operations whose execution requires a particular mathematical skillset. Moreover, an assessment of these operations is made on the basis of discernible rules, in this case the rules governing the correct manipulation of mathematical symbols. But does the fact that the cognitive agent performs the right kinds of operations ensure that she succeeds in obtaining understanding? A closer look reveals that this is not the case: Facing the challenge of applying the Lorentz transformations to two quadruples of coordinates, a cognitive agent could behave in all the ways we would expect her to behave. Yet, if all the agent does is to mechanically reproduce a series of pre-memorized operations, then this would hardly count as a display of genuine understanding. Hence, in order to distinguish such cases of “counterfeit understanding” from cases of genuine understanding, cognitive agents are also required to be able to construct a mental representation of whatever it is they seek to understand. 5 Manipulating this representation allows the agent to produce variations of the initial representation: For instance, the agent could apply the Lorentz transformations to different quadruples of coordinates; or she could use varying representations to detect and correct errors in her derivations. Hence, the upshot of these considerations is that the performability of certain operations is not sufficient for genuine understanding. A cognitive agent must also be able to construct a mental representation to which the relevant operations can be applied.

Let’s assume that a cognitive agent is able to construct a mental representation of the mathematical demonstration of the relativity of simultaneity. And let’s also assume that the agent is able to manipulate this representation by performing the right kinds of mathematical operations. If these two conditions are met (and if the manipulationist account outlined so far is correct 6 ), the strategy to derive the relativity of simultaneity from the mathematical formalism of SR yields understanding. Yet, my suggestion is that, given the context in which the relativity of simultaneity is of primary interest, this strategy yields the wrong kind of understanding , especially for cognitive agents who are not yet familiar with the specifics of SR. The reason for this verdict is simple: Although you can’t have the former without the latter, physics is more than pure mathematics. Starting from the equations of the Lorentz transformations, a cognitive agent who is sufficiently conversant with mathematics will have no trouble performing the correct operations to obtain the desired results. She can do this, however, without paying attention to the physical meaning of the symbols she is manipulating, or, even more fundamentally, without considering whether the symbols have extra-mathematical meaning at all. But since the point of the whole exercise is not to test or sharpen our mathematical abilities, the kind of mathematical understanding that results from manipulating abstract symbols is at best indirectly relevant to the agent’s physical understanding of SR.

We may summarize the previous paragraph as follows: Although demonstrating the relativity of simultaneity on purely mathematical grounds yields mathematical understanding, this kind of understanding is not sufficient to promote the physical intelligibility of SR. One of the main reasons is, as I have argued, that a mathematical demonstration leaves the physical meaning of the abstract symbols undetermined. It is this indefiniteness that makes it hard for a cognitive agent to understand the physical significance of the results, even if she possesses the mathematical skills to solve the equations with ease. Of course, one may wonder whether this drawback could be overcome by simply laying down definitions for the symbols and concepts used. Suppose, for instance, that a cognitive agent is able to perform the mathematical operations, but is unfamiliar with the physical concept “reference frame”. Could the cognitive agent gain physical understanding if she were told that a reference frame is defined as a “set of coordinates used by an observer to describe space-time” (Ellis and Williams 1998 , p. 27) or as “a coordinate grid equipped with a set of clocks located at the grid intersections and synchronized” (Faraoni 2013 , p. 16)? Although it seems too strong of a claim that textbook definitions of this kind are entirely without epistemic significance, the information they provide hardly suffices to render the physical implications of the mathematical derivations intelligible. The reason is that knowing the definition of “reference frame” does not entail the practical knowledge that is necessary to do epistemic things with reference frames, e.g. to map them onto real-world scenarios in order to solve empirical puzzles. This point has been emphasized by thinkers such as Michael Polanyi ( 1998 ) or Thomas Kuhn: Since textbook definitions typically do not specify how and under which conditions abstract symbols and concepts can be applied to reality, a student learns their physical meaning “less from the incomplete though sometimes helpful definitions in his text than by observing and participating in the application of these concepts to problem-solution” (Kuhn 1970 , p. 47). 7

As mentioned earlier, it is a common practice in physics textbooks to give a mathematical derivation of the relativity of simultaneity only after the basic idea has been introduced through a TE. We are now in a position to explain why this is so. A mathematical demonstration falls short of providing physical understanding because mathematical operations alone are not suited for consolidating the physical meaning of the abstract symbols and concepts. Yet, it is precisely this consolidation of physical meaning that is accomplished by TEs in a very efficient and undemanding way (cf., on this point, also Stuart 2017 , pp. 22–24). Consider again a cognitive agent who is unfamiliar with the concept of a reference frame. While, as we have seen, textbook definitions are only of limited value, performing Einstein’s train TE puts the agent in a position to grasp the physical meaning of the concept in an intuitive, almost playful manner. How does the TE achieve this? In order to perform the TE, the cognitive agent must begin with constructing a mental representation of an imaginary scenario. Like with most other scientific TEs, the scenario is built up from familiar every-day objects such as wagons, train tracks and wave crests that represent propagating light flashes. Once the mental representation of the TE-scenario is set up in the expected manner, the cognitive agent is required to let the scenario unfold, and to record the outcome from two different perspectives. Upon doing this, she not only realizes that the temporal order of the incoming light flashes varies depending on her location within the imaginary scenario. By determining two origins from which the same occurrence is qualitatively described, the cognitive agent also performs the necessary operations to grasp the basic idea of a (non-technical notion of) reference frame.

On the view defended here, TEs facilitate physical understanding by achieving two related objectives. The first is to consolidate the meaning of abstract concepts by requiring the cognitive agent to perform operations through which these concepts are mapped onto mental representations of scenarios that are built up from familiar objects of our every-day experience. 8 The point of this exercise is to bring unfamiliar concepts under the agent’s cognitive control: The agent comes to understand a new concept by constructing a mental representation of a scenario that she already knows and to which the unfamiliar concept can be successfully applied. If the agent succeeds, she is in a position to do further epistemic things with the newly acquired concept. For instance, by rebuilding the mental representation of the TE-scenario with cars instead of trains, the agent could apply the concept “reference frame” to a scenario that is sufficiently similar but not identical with the original one. Or the cognitive agent could work through a series of imaginary scenarios with decreasing degrees of specificity in order to establish semantic connections between the mathematical formalism and empirical reality. 9

Once the necessary conceptual resources are in place, it becomes possible to proceed with the second objective. Now that the world is sufficiently well represented conceptually, the cognitive agent can actually perform the TE in order to clarify the consequences that result from applying the newly acquired theoretical framework. There are two reasons why TEs are particularly well suited for this purpose: On the one hand, TEs rely on highly simplified environments for their execution. It is through the omission of uncontrollable factors and outside influences that TEs deliver results with perfect precision and clarity. And this makes it significantly easier to focus on the implications of the theory without being sidetracked by ambiguities with which real experiments are always fraught. On the other hand, TEs make it fairly easy to distort reality in ways that help closing the gap between theoretical concept and empirical fact. It is, for instance, well known that many relativistic effects such as time dilation or length contraction are almost imperceptible at everyday speeds. The train TE makes up for this by stipulating a world in which the succession of incoming light waves is straightforwardly observable without the need for sophisticated measuring devices.

Let me briefly summarize the main results of this section. The process of facilitating physical understanding through TEs involves two key aspects: While constructing a mental representation of the TE-scenario helps fixing the meaning of the relevant theoretical concepts, the actual performance of the TE clarifies the consequences of applying the newly acquired framework. Note, however, that, on the view proposed here, TEs must be actively done and not just passively “consumed”: It is, of course, true that the TE-narrative contains most of the information that is relevant for how and in which imaginary world the TE is supposed to be executed. But if understanding crucially depends on the possession of a mental representation of whatever it is one seeks to understand, cognitive agents are required to actively construct the TE-scenarios in their mental spaces. 10 Let us now, with these remarks as a backdrop, turn to Joe W. Haldeman’s award-winning novel The Forever War .

The Forever War

TFW is a military science fiction novel that was first published in 1974. Its author, Joe W. Haldeman, received a degree in physics and astronomy from the University of Maryland in 1967. In the same year Haldeman was drafted into the US Army and served as a combat engineer in Vietnam. He was severely wounded in battle and received a Purple Heart for his service. TFW is a semi-autobiographical text in which Haldeman reflects on his own wartime experiences as well as on his experiences as a returning veteran (cf. Gordon 2006 ).

Like Haldeman himself, the main protagonist of TFW, William Mandella, is conscripted by the UNEF (United Nations Exploratory Force) after receiving his degree in physics and astronomy. The year is 1997 and humanity is at war. Yet, the war humanity is fighting in the parallel universe of TFW is quite different from the wars we know. Twelve years earlier, in 1985, scientists had confirmed the hypothesis according to which separate points in spacetime are linked by Einstein–Rosen-bridges or, as they are more familiarly known, “wormholes”. Yet, far from being a purely theoretical success, this discovery had far-reaching practical consequences, for scientists also found a way to enter wormholes through what Haldeman calls “collapsars”:

Just fling an object at a collapsar with sufficient speed, and out it pops in some other part of the galaxy. It didn’t take long to figure out the formula that predicted where it would come out: it travels along the same “line” (actually an Einsteinian geodesic) it would have followed if the collapsar hadn’t been in the way—until it reaches another collapsar field, whereupon it reappears, repelled with the same speed at which it approached the original collapsar. Travel time between collapsars... exactly zero. (Haldeman 1974 , p. 7)

With this knowledge in hand, it was possible to cover the vast distances of interstellar space, and humanity could finally colonize the galaxy. But it wasn’t until long that something unexpected happened: a ship with human colonists disappeared and UNEF came to the conclusion that it was destroyed by a hitherto unknown alien race, called the “Taurans”. Humans retaliated and this led to the interstellar conflict into which the main protagonist William Mandella—a somewhat resigned character with pacifist leanings—is thrown.

The fact that humanity is fighting against aliens is not the only reason why the war in TFW is different from the wars we know. For our purposes here, an even more important reason is that the frontline of the conflict can only be reached through collapsar jumps. Now, it is not the jumps themselves that cause problems—as we have seen, spaceships just need to enter a collapsar with sufficient speed and at the right angle in order to re-appear at the other end of the galaxy without any loss of time. The problem is rather to get to the collapsars in the first place. Collapsars are few and far between and in order to cover the vast distances of empty space, spaceships must travel for significant periods of time with velocities close to c . However, at such high velocities a peculiar relativistic effect known as time dilation becomes manifest. Since this effect plays a crucial role in TFW, and since Haldeman simply stipulates the existence and ramifications of time dilation, it should be discussed in a bit more detail.

The breakdown of absolute simultaneity is but one of several perplexing consequences of SR. Another is time dilation , i.e. the phenomenon that a relatively moving observer will measure time differently from an observer at rest. In light of what has been said in the previous section, the best way to make this phenomenon intelligible is by introducing an epistemic practice to fix the meaning of the relevant concepts, and by then working through a TE.

Imagine an idealized timekeeping device, a so-called light clock. A light clock consists of a rod with a mirror at each end. A light pulse is traveling back and forth between the mirrors, and every time the light pulse hits the bottom mirror, the clock ticks. Figure  3 shows how a light clock appears to an observer if both the clock and the observer are at rest.

Light clock at rest

Since the light signal traces out a path with the length of 2 L , the period of the clock is given by

But what happens if the light clock is set into rapid motion perpendicular to the rod? Now that the rod is moving, the light pulse must chase after the opposing end as it travels along the x-axis with velocity v . As can be readily seen from Fig.  4 , this is to say that the light signal must cover a longer distance before it returns to its starting point. But since, according to the light principle, c is always constant, this also means that the light pulse needs more time to travel between the mirrors. As a consequence, the light clock ticks less often in the judgment of an observer who does not move with the clock. For an observer at rest, the period of the moving clock is given by

where D is the hypotenuse to the perpendicular distance L . Using Pythagoras’ Theorem to calculate the exact length of D , we realize that the moving clock ticks at exactly half of the speed of a resting clock if v = 0.866 c . But even without doing any sums, the outcome of the TE should be apparent: A clock that is moving relative to an observer will be measured to tick slower than a clock at rest.

A light clock that is moving relative to an observer

Of course, it might be tempting to assume that this result only affects timekeeping devices that rely on light. This, however, is not the case. On pain of violating the principle of relativity, every physical system that is a time-measuring device of sorts must slow down in keeping with the light clock. This is true not only of more traditional timekeeping mechanisms such as wound-up springs, swinging pendulums or oscillating crystals. Time dilation also affects the human metabolic system whose processes will slow down at precisely the same rate as the light clock. So, if we put a light clock and a living person on a spaceship traveling at 0.866 c , then not only will the light clock be measured to tick at exactly half the speed of a resting lock. The person’s metabolism will slow to 50% of its normal rate as well, even though the slowing of all physical systems will be indiscernible from within the spaceship. However, if the person returns to earth after what we in the rest frame find to be one year, the person will have biologically aged only six months. Note also that the magnitude of this effect increases dramatically as velocities approach c : For instance, after an earth-year long voyage at 0.999 c , a space traveller will have aged just a bit over 16 days. 11

Let us return to the alternative universe of TFW. As I have pointed out, the frontline of the interstellar conflict can only be reached through collapsars, and in order to reach these, spaceships must cover several lightyears at velocities close to c . This, however, has serious repercussions for the soldiers who fight in this war. For instance, after Mandella returns from his first assignment after less than two years, he is handed out a table of organization (T/O) that almost pulls the rug from under his feet—and remember that his army career had already started in 1997:

I couldn’t get over the “20 Mar 2007” at the bottom of the T/O. I’d been in the army ten years, though it felt like less than two. Time dilation, of course: even with the collapsar jumps, traveling from star to star eats up the calendar. (Haldeman 1974 , p. 70)

In light of what we have said about the implications of SR, it is not hard to figure out what happened. Mandella has spent the majority of his army career at velocities close to c . 12 As a consequence, time has passed at a much slower rate in his reference frame, de-syncing him from the passage of time of his fellow humans on earth. While Mandella is only less than two years older after his first mission, ten full years have passed for the rest of humanity. In the beginning, he is not particularly concerned. For instance, since the remuneration of soldiers is calculated on the basis of earth-years, Mandella surmises that he will be a made man after his second mission:

After this [second] raid, I would probably be eligible for retirement with full pay—if I lived through the raid, and if they didn’t change the rules on us. A twenty-year veteran, and only twenty-five years old. (Haldeman 1974 , p. 70)

But when Mandella returns to earth after a series of follow-up missions, he realizes that all the money in the world cannot compensate for the feeling of alienation he is experiencing. The year is 2458 and the war has been raging for almost half a millennium. The earth Mandella has left in the 1990s has not only evolved—it has ceased to exist. Social and political order have changed dramatically. For instance, in order to fight over-population, racial tensions and diseases, UNEF’s “Eugenics Council” has made heterosexual relationships and non-artificial reproduction a punishable offense (Haldeman 1974 , p. 157). All babies are genetically engineered, brought up in government controlled crèches and trained to serve UNEF’s main goal, that of continuing a war that has already lost its military purpose, but without which earth’s economy would collapse (Haldeman 1974 , p. 215). Quite generally, society has become a soulless dystopia in which people are treated as disposable commodities. On their seventieth birthday citizens receive a rating that is based on their estimated importance for society. If, like in the case of Mandella’s mother, the rating is zero, they are no longer eligible for any kind of medical care (Haldeman 1974 , pp. 118–119).

Although Mandella has difficulty fitting into society, and even though most of his fellow humans view him with suspicion as well, his wartime heroics are heavily exploited by the UNEF-controlled media. Mandella—meanwhile by far the oldest surviving soldier and promoted to the rank of Major General—is expected to take command of his own strike force. But even army life leaves him with a feeling of isolation. Mandella is disliked by his subordinates for several reasons. His heterosexuality is considered an emotional dysfunction that is only tolerated because of his merits on the battlefield. And since he is hundreds of years older than everyone else in the common galactic frame, Mandella’s soldiers are required to learn twentieth-century English in order to be able to communicate with him. Mandella, who baffles his comrades with jokes about long-forgotten figures such as John Wayne (Haldeman 1974 , p. 149), is as alien to his new lifeworld as Christopher Columbus or Hieronymus Bosch would be to ours.

For some time, Mandella has one last link to the world he knew. He is in a relationship with Marygay Potter, a female soldier who also entered the UNEF in the 1990s. But when the war is on a knife-edge, Mandella and Potter receive orders to embark on different missions in different parts of the galaxy. Never has SR been more gut-wrenching:

For a long time we couldn’t say anything. “I’m going to protest,” I said finally, weakly. [...] She was still struck dumb. This was not just a separation. Even if the war was over and we left for Earth only a few minutes apart, in different ships, the geometry of the collapsar jump would pile up years between us. When the second one arrived on Earth, his partner would probably be a half-century older; more probably dead. We sat there for some time, not touching the exquisite food, ignoring the beauty around us and beneath us, only conscious of each other and the two sheets of paper that separated us with a gulf as wide and real as death. We went back to Threshold. I protested but my arguments were shrugged off. I tried to get Marygay assigned to my company, as my exec. They said my personell had all been allotted. I pointed out that most of them probably hadn’t even been born yet. Nevertheless, allotted, they said. It would be almost a century, I said, before I even get to Stargate. They replied that Strike Force Command plans in terms of centuries. Not in terms of people. We had a day and a night together. The less said about that, the better. I wasn’t just losing a lover. Marygay and I were each other’s only link to real life, the Earth of the 1980s and 90s. Not the perverse grotesquerie we were supposedly fighting to preserve. When her shuttle took off it was like a casket rattling down into a grave. (Haldeman 1974 , pp. 138–139)

Physical and existential understanding

TEs facilitate understanding by requiring cognitive agents to construct mental representations of imaginary scenarios through which theoretical consequences can be made intelligible in an intuitive and non-technical manner. In order to achieve this aim, imaginary scenarios must be designed so as to strike a balance between familiarity and strangeness (Gooding 1992 , p. 283): If, on the one hand, imaginary scenarios would not consist of familiar objects of everyday experience, cognitive agents would find it difficult to establish meaningful connections between theory and empirical fact. If, on the other hand, imaginary scenarios would not deviate from empirical reality through abstractions and idealizations, cognitive agents would fail to identify unforeseen theoretical consequences that in many cases remain hidden under normal lifeworld conditions. Einstein’s train TE is a case in point: We are familiar with objects such as wagons and train tracks. And we have no difficulty in constructing varying mental representations in which we perceive the unfolding scenario from two different viewpoints. Yet, if we introduce certain abstractions and idealizations into the imaginary scenario, we put ourselves into a position to make a far-reaching consequence of SR intuitively understandable.

On the view proposed here, much of what can be said about scientific TEs is also true of science fiction novels such as TFW. Like Einstein’s train scenario, the fictional world of TFW resembles ours in several important respects. For instance, we are familiar with the countless reports of the feelings of alienation and isolation that were common among returning Vietnam veterans. While soldiers from earlier conflicts were generally welcomed as heroes in what was seen as a necessary cause, many of those who had served in Vietnam returned to a society which had changed deeply during their absence. The US were greatly divided over the war, and the strong antiwar sentiment that could be felt all across the country was just one facet of a larger process of societal change (Tischler 2002 ). Apart from the physical and mental scars of war, it was this transformation of society that made it notoriously hard for Vietnam veterans to re-adapt into civilian life. Although it would be pretentious to think that we can recreate the emotional and social hardships of veterans without having experienced war and its aftermath ourselves, it seems safe to say that we can relate to the underlying feelings of isolation and alienation—feelings that are so central to human existence that we have no difficulty in identifying with them.

Another phenomenon that connects the fictional world of TFW with ours is the experience of parting ways with a loved one. We are familiar with the feelings of sadness and loss when we bid farewell at a train station or departures hall. And we can imagine how much stronger these feelings must be if the loved one not just goes on a business trip, but embarks on a mission that involves life-threatening risks. Like in the earlier example of returning Vietnam soldiers, we are dealing here with what could be called “existential feelings”. By “existential feeling”, I mean mental and emotional experiences that are so deeply embedded in human nature that they appear to be invariant across cultures and times. They are an essential part of the human condition, which is also why we can relate to them fairly easily. 13

Upon reading TFW, we are invited to immerse ourselves in a fictional world that is sufficiently similar to ours. The main protagonist, from whose perspective the story is told, undergoes emotional experiences to which we can relate because of their existential character. However, it is through the introduction of several omissions 14 and counterfactual deformations that the cognitive value of engaging with the fictional world of TFW is increased significantly. Instead of just offering a more or less realistic rendition of the emotional hardships of a returning soldier, TFW helps us to understand how existential feelings of alienation, isolation or loss would be amplified if technological innovations made relativistic effects like time dilation part of our every-day lifeworld. Even if we are fortunate enough to have never experienced war first-hand, we can relate to the former Vietnam soldier Larry Heinemann, who recalls that, after returning to the US, “I had the distinct feeling (common among returning veterans I think) that this was not my country, not my time” (Heinemann, quoted in Isaacs 1997 , p. 12). However, after having immersed ourselves into the fictional world of TFW by putting ourselves into the shoes of William Mandella, we understand how much stronger this sentiment must be if the war zone was not on the other end of the globe, but lightyears away on the other end of the galaxy. While Heinemann’s statement might be seen as a slightly exaggerated figure of speech, it would be literally true if uttered by William Mandella.

Seen from this perspective, then, science fiction novels such as TFW indeed function much like TEs: In order to gain cognitive purchase from TFW, the reader must construct a mental representation of a fictional world which is designed to strike a balance between strangeness and familiarity. Once the reader has successfully immersed herself into this world by empathizing with the main protagonists, she can observe how the narrative unfolds according to its own inner logic. Upon doing this, the reader puts herself into a position to make certain unforeseeable consequences of SR intelligible: The reader comes to understand what it would mean for human beings to inhabit a world in which relativistic effects like time dilation directly interfere with their everyday lives. 15

It is now possible to address an issue to which I have already alluded in the opening section. On the view proposed here, TEs in physics aim at what I have called “physical understanding”. Following the results of Sect.  2 , the process of facilitating physical understanding involves two key aspects: The first is to construct a mental representation of an imaginary scenario onto which certain theoretical concepts can be mapped. It is in this way that we use TEs to fix the physical meaning of concepts by specifying their referents. Once the theoretical concepts are brought under the agent’s cognitive control, the second stage consists of applying the newly acquired framework to the representation of the imaginary scenario, and record the outcome. Here, the point is to make certain consequences of the theory intuitively accessible within the confined space of the laboratory of the mind. Given this two-tiered structure, it is clear that the scope of scientific TEs is usually focused to what one could call “inner-theoretical clarification”: The purpose of most scientific TEs is to increase our understanding of the inner workings of theories as well as their immediate empirical consequences. 16 TEs achieve this aim by establishing meaningful connections between abstract concepts and empirical fact, and by exemplifying the consequences of applying the theories to their intended target domains (cf. Stuart 2017 ).

Yet, looking at science fiction novels, a slightly different picture emerges. To be sure, if we wish to gain cognitive purchase from a novel like TFW, we are also required to actively participate in a distinctively designed imaginary scenario, for instance, by imagining to see the world of TFW through William Mandella’s eyes. However, the point of this exercise is neither to consolidate the physical meaning of abstract concepts, nor to exemplify certain theoretical consequences. Throughout TFW, Haldeman simply stipulates what the ramifications of time dilation are—beyond that, the narrative does nothing to promote physical understanding of why time dilation comes about. This might seem to undermine the analogy between science fiction and TEs at first. But it is important to realize that TFW does promote our understanding of SR, albeit in a way different from Einstein’s train or the light-clock TE. Instead of clarifying the inner workings and immediate empirical consequences of SR, TFW makes intelligible how certain implications of SR would affect the emotional and social dimensions of human existence . 17 Hence, while scientific TEs such as Einstein’s train focus on inner-theoretical clarification and physical understanding, science fiction novels like TFW aim at promoting the existential understanding of SR. If written in a scientifically responsible manner, 18 science fiction has thus the potential to increase our understanding of what it means for us, as human beings, to live in the kind of world our increasingly arcane scientific theories purport to describe.

There is one final point I would like to address. In Sect.  2 , I have introduced a distinction between mathematical and physical understanding. Following the idea that the performability of different epistemic practices result in different kinds of understanding, it seems reasonable to assume that existential understanding is the result of a distinctive epistemic practice as well. Hence, the question arises: what can we say about the mental operations that must be performed in order for existential understanding to occur, and how are they different from those that facilitate physical understanding?

When a cognitive agent performs a scientific TE, she is required to construct a mental representation of a scenario onto which certain theoretical concepts can be mapped, and through which certain theoretical consequences can be exemplified. In many cases—like Einstein’s train or the light-clock TE—it is also necessary to imagine an observer from whose perspective the outcome of the TE is perceived. On closer inspection, however, the role of the observer turns out to be confined to that of a mere data collector. For instance, the outcome of Einstein’s train TE does not depend on whether the cognitive agent imagines the observers to be herself, other conscious beings or measurement apparatuses. As long as the temporal order of the incoming light flashes is correctly recorded, the specifics of the imagined observer are entirely irrelevant for the purpose of facilitating physical understanding.

Yet if we look at science fiction novels such as TFW, things stand differently. To be sure, in order to gain cognitive purchase from TFW, we are also required to construct a mental representation of a fictional world that is designed to strike a balance between strangeness and familiarity. But if all we were to imagine was a world that is technologically superior to ours, this would lead us nowhere as far as existential understanding is concerned. The reason for this is straightforward: If my analysis is correct and if the aim of TFW is to make intelligible how certain consequences of SR would affect the emotional and social dimensions of human existence , then, of course, the fictional world of TFW must be imagined so as to contain beings who are able to undergo experiences that are relatable due to their existential character. For instance, not much could be learned from TFW if we replaced William Mandella with Lieutenant Commander Data from Star Trek: The Next Generation . 19 And this tells us something significant about the mental operations that must be performed in order to gain cognitive purchase from TFW: In order for existential understanding to occur, we are required to construct a mental representation of William Mandella in his environment. In part, this means to imagine a technologically advanced world in which interstellar travel is a reality. Yet, even more important, it also means to construct a representation of Mandella’s system of thoughts, beliefs, desires and feelings, and to identify with this representation through what Goldman has called “enactment imagination” (Goldman 1998 ). This is to say that we are required to use the faculties of imagination to recreate the phenomenology of particular mental states by producing facsimiles of the selected states in our own minds. So, for instance, when we consider the scene in which Mandella watches the takeoff of his spouse’s shuttle, we are required to take up his perspective by enacting or re-creating feelings of loss and sadness, feelings to which we can relate due to their existential character. The cognitive surplus that can be gained from TFW is achieved by way of manipulating the mental representation: The process of enactment imagination that makes the identification with the main character possible is driven by background knowledge about the specific conditions under which Mandella watches his partner’s departure. Since we know that time dilation will most likely turn their farewell into a final parting, we come to understand how certain consequences of SR would affect the human lifeworld by amplifying existential feelings such as loss, sadness or isolation.

Let me conclude this section with a summary. On the view defended here, the kind of physical understanding that is brought about by TEs and the kind of existential understanding that is facilitated by science fiction novels are structurally similar in several important respects. To begin with, TEs and science fiction novels are similar in that neither pay epistemic dividends if they are merely passively consumed. In order to yield understanding, both require their recipients to perform operations whose aim it is to construct mental representations that are specifically designed to strike a balance between strangeness and familiarity. The productive interplay between strangeness and familiarity is another common trait that is instrumental to the epistemic outcome in both areas: If the respective mental presentations are too strange, then cognitive agents will find it hard to establish meaningful connections between the already familiar and that which is still beyond their cognitive grasp. If, on the other hand, the respective mental representations are too familiar, then they will fail to disclose anything of epistemic interest. Hence, it is only if “there is enough strangeness to disturb and enough familiarity to be accessible” (Gooding 1992 , p. 283) that both TEs and science fiction novels can be successful in exemplifying the consequences of abstract scientific theories in an intuitive, quasi-sensory and non-technical manner. Once intelligibility is achieved in this way, cognitive agents are also in a position to deepen their understanding by further manipulating the respective mental representation. In the case of TEs, cognitive agents could, for instance, proceed by manipulating the imaginary scenario so as to produce variations with decreasing degrees of specificity. It is in this way, as we have seen, that TEs can help to make the physical meaning of mathematical concepts intelligible. In the case of science fiction novels, cognitive agents could proceed by manipulating the initial mental representation so as to produce “mixed narratives”, i.e. narratives that combine fictional elements with actual memories and experiences. For instance, upon immersing myself into the parallel universe of TFW, I could reflect on how my family life would have been affected if my last research stay had not led me to another continent, but to a solar system thousands of light years away from Earth.

Despite all similarities, however, one must not lose sight of the differences between the kinds of understanding that are facilitated by TEs and science fiction novels. In order to fix the meaning of abstract concepts, many TEs require us to construct imaginary scenarios in which familiar objects of every-day experience interact under hypothetical or counterfactual conditions. Once the imaginary scenario is set up in the expected manner, cognitive agents can then let the scenario unfold in order to make the consequences of applying the newly acquired theoretical framework intelligible. At first glance, this way of proceeding does not appear to be significantly different from what happens when we gain cognitive purchase from a science fiction novel such as TFW: Here too, we are required to construct a mental representation of a fictional world in which hypothetical or counterfactual conditions hold, and through which certain consequences of SR become intuitively intelligible. However, while the focus of TEs is on familiar quasi-empirical objects and the conceptual frameworks that are being used to describe them, science fiction novels like TFW are primarily concerned with human beings who undergo familiar existential feelings while being exposed to an environment in which the consequences of SR are directly experienceable. This difference in focus is reflected in the different kinds of operations that underlie physical and existential understanding: In order to obtain the latter, cognitive agents must empathize with William Mandella by re-creating familiar feelings of loss, alienation or sadness. If the mental representation of Mandella’s system of thoughts, beliefs, desires and feelings is integrated into the parallel universe of TFW, we come to understand how certain consequences of SR would affect the social and emotional dimensions of human existence.

Concluding remarks

Edmund Husserl is famous for the claim that modern scientific culture is haunted by a deeply-rooted crisis (Husserl 1970 ). Despite all their sophistication and effectiveness, the special sciences—and mathematical physics in particular—have become increasingly remote from human experience. As a consequence, non-scientists find it more and more difficult to understand what modern theories tell us about the world of every-day practice. And, according to Husserl, this results in a growing skepticism about the principal worth of the scientific enterprise and thus in a menacing irrationalism: “In our vital need—so we are told—this science has nothing to say to us.” (Husserl 1970 , p. 6)

Husserl—a German philosopher of Jewish descent—wrote these lines during the 1930s and hence during a time when the forces of nationalism, fanaticism and anti-scientific obscurantism already threw a dark shadow over Europe. Yet, in light of the current rhetorics of “alternative facts” and “post-truth politics”, it is hard to not feel addressed by Husserl’s message. The authority of science is again coming under fire and it is reasonable to suspect that ignorance about what science is and says is part of the problem. Forbidding mathematical formalisms, highly complex technological apparatuses and inaccessible technical jargons are among the hurdles that prevent laypersons not only from grasping the content of particular scientific theories; the increasingly common trend to reject, say, climate science because “it is only a model” attests to an even more fundamental ignorance about the very nature of scientific reasoning. Now, although I am not suggesting that TEs and science fiction alone will be able to save the day, I do believe that they could go some way toward closing the gap between the general public and professional scientists. As we have seen, TEs are highly efficient tools for conveying scientific ideas to non-experts. Since, in most cases, little pre-existing knowledge is necessary for their execution, and since most TE scenarios consist of familiar objects of every-day experience, TEs prove epistemically rewarding to a wide array of cognitive agents. What is more, since TEs must be actively done and not just passively consumed, TEs afford a sense of accomplishment that motivates cognitive agents to cultivate their critical thinking and analytical skills. Given all this, it is not surprising that TEs have been praised for their positive impact on science education (cf., e.g., Gilbert and Reiner 2010 ).

However, there is an important sense in which the epistemic reward facilitated by TE is only partial. If my analysis is correct, then one of the primary aims of many TEs is to consolidate the meaning of abstract concepts by requiring the cognitive agent to perform operations through which these concepts are mapped onto mental representations of scenarios that consist of familiar objects of our every-day experience. Yet, even though they are built up from familiar objects, most TE scenarios are still very far removed from the world in which we, as human beings, live our daily lives. As water buckets in empty universes and cars at close-to-light-speed velocities attest, much of the epistemic force of TEs stems from the fact that familiar objects are imagined under conditions that, more often than not, differ radically from those prevailing in the lifeworld of every-day practice. Now, to be sure, my point is not that the strangeness of most TE scenarios is a reason for concern. Quite the opposite, the deliberate distortion of reality is, as I have argued, crucial for the epistemic outcome of TEs. But the drawback of invoking imaginary scenarios in which fairly strange conditions hold is that cognitive agents might find it hard to see how anything that happens under such conditions has practical relevance for the proverbial “man on the street”. To put it bluntly: It may be an amusing pastime to fix the meaning of abstract concepts by pondering over cars that move with velocities close to c . But what difference do these concepts make for someone who is stuck in morning traffic six times a week?

While TEs are a highly effective tool to make scientific theories intelligible, they do little to counterbalance the increasingly common sentiment that much of today’s science is too detached from the real world to make a tangible impact on problems real people face. In my view, it is precisely at this juncture that science fiction could come to the rescue. To be sure, science fiction novels also take place in strange fictional worlds that differ from ours in more or less drastic ways. However, since novels such as TFW aim at existential rather than at physical understanding, their epistemic utility does not primarily depend on imagining strange scenarios, but on constructing mental representations of desires and feelings real people could have, and to which we can relate due to their existential character. William Mandella is imagined as such a real person who experiences emotions that virtually everyone of us has experienced at some point in life. Using the imagination to put Mandella into a specifically designed environment not only allows us to understand how certain consequences of scientific theories would transform our lifeworld by amplifying familiar feelings such as loss or alienation. By empathizing with a real person who acts under conditions that, although not the ones we are used to, are specified by our best scientific theories, we also come to understand that the seemingly arcane “world of science” might only be a few technological innovations away from becoming the world in which our daily lives unfold. Seen from this perspective, then, TEs and science fiction indeed appear to be natural bedfellows: While the former are highly effective tools for facilitating physical understanding of theories and/or the phenomena in their domain, the capacity of science fiction to generate existential understanding could help to give science a more human face.

Acknowledgements

Open access funding provided by Linköping University. Earlier versions of this paper were presented at conferences on thought experiments and fiction in Naumburg, Germany, and Paris, France. I would like to thank the organizers and the respective audiences, as well as Jim Brown, Sebastian Luft, Axel Maas, Pierre Saint-Germier and two anonymous referees for their helpful remarks and suggestions. Special thanks are due to Mike Stuart whose input over the years had a tremendous impact on my views on thought experiments and understanding, to Marian David for introducing me to the works of Joe Haldeman, and to Werner Wiltsche for helping me with the figures. Finally, I thank the Austrian Research Fund (FWF) for a generous grant in support of this work (Project Number: P31758).

1 This line of argument can also be found in the debate about TEs. For instance, Jim Brown writes that “explanation [is] an objective feature of theories [whereas] [u]nderstanding is more subjective, a psychological feature of ourselves” (Brown 2014 , p. 372).

2 Of course, much depends on what one takes understanding to be. For instance, if one subscribes to the view that understanding consists in the “grasping of relations between items of information” (Kvanvig 2003 , p. 197), the cognitive outcome of my reading of Orwell’s novel is the acquisition of new knowledge, namely knowledge about the relations between existing items of factual information about the world. The account of understanding that I am advocating will be outlined in the next section.

3 Note, however, that Hills’ account is more narrow than the manipulationist approach I am advocating here. While Hills agrees that understanding is a certain kind of ability or know-how, she is only concerned with the intellectual abilities that are necessary to give explanations of why P .

4 Of course, the assumption here is that the mental representation captures the relevant features of what is being represented. If this is the case, the ability to manipulate the mental representation of P prefigures the possibility of successfully manipulating P . It should also be noted that the notion of manipulation that is at work here must be sufficiently inclusive to incorporate a broad range of disparate objects. If the object of understanding is, say, an engine, “manipulation” will amount a re-arrangement, replacement or patching of its functional parts. If the object of understanding is, say, a mathematical proof, “manipulation” will predominantly consist in drawing inferences. As we shall see in more detail later, “manipulation” in the case of TEs usually amounts to the construction and re-arrangement of imaginary scenarios and to the ability to draw meaningful inferences from them.

5 As one reviewer has noted, it might not be immediately clear why the the ability to construct a mental representation solves the problem of counterfeit understanding. Let me illustrate the basic idea by means of an example: Suppose you want to test student A’s and B’s understanding of elementary algebra by asking them to give a step-by-step solution of the equation 2 x + 1 = 3 . But imagine furthermore that, since one of your test sheets have miraculously disappeared, you have reason to believe that one of your students already knew the question prior to the exam. During the exam, both students perform the same operations: after moving the “ + 1 ” from left to right, making it a “− 1”, they move the “2” from left to right, making it a “ 1 2 ”, and finally obtain the solution x = 1 by simplifying the right side. Yet, even though both students have displayed the exact same ability to perform according to set standards, you want to make sure that neither of them has merely simulated understanding by replicating a pre-memorized solution. Several strategies suggest themselves: you could, for instance, inquire as to why the “2” from step 2 becomes a “ 1 2 ” and not a “ - 2 ”; or you could ask your students to solve a different, but sufficiently similar equation like 3 x + 5 x + 4 - x + 7 = 88 . But why is it that such follow-up questions are an appropriate way to distinguish counterfeit from genuine understanding? In my view, and in line with Wilkenfeld’s views on the matter, the most plausible answer is that these follow-up questions are designed to look for cognitive structures that prefigure worldly abilities like solving equations on a blackboard. The most promising candidate for such cognitive structures are mental representations of the object one seeks to understand, in this case a mental representation of the relevant parts of elementary algebra with which one can do certain things, and which must stand in the right relations with other mental representations like that of the relevant parts of arithmetic. The prediction that follows from this hypothesis is that a student who only replicates pre-memorized operations will not be able to answer the follow-up questions in a satisfactory manner. A student who is able to construct a mental representation of the relevant parts of algebra, on the other hand, will not only be able to solve the initial equation. She could also solve indefinitely many other algebraic equations, contemplate alternative solution-strategies before actually writing one of them down, talk about elementary algebra in her own words, or perhaps even—if the mental representation of algebra is sufficiently well integrated into her global representation—apply algebra to empirical situations such as weights representing “ 2 x + 1 ” and “3” on each pan of a balancing scale. Cf., for empirical studies detailing how different areas of mathematics are mentally represented in the human brain, e.g. Greeno ( 1983 ), Dehaene ( 1999 ), and Dreyfus ( 2002 ).

6 While I believe that manipulationism is the most promising approach, it is beyond the scope of this paper to defend it against possible alternatives. For criticisms of manipulationist accounts of understanding, cf., e.g., Khalifa ( 2017 , chapter 3).

7 I consider this to be a well-established historical fact. For instance, in his historical account of the global dispersion of Feynman diagrams in post-war physics, David Kaiser describes how their reception in the Soviet Union was hindered by the cold war separation of Western and Soviet physicists. Although Soviet theorists had access to published papers, travel bans “deprived them of any chance for informal, face-to-face exchanges with physicists on the other side of the iron curtain”. This lack of personal contact made it impossible for them “to pick up and use Feynman diagrams in anything like the ways their colleagues in the United States, Great Britain, and Japan did” (Kaiser 2005 , p. 150).

8 As one reviewer has pointed out, there are exceptions to this generalization, most notably the famous Einstein–Podolsky–Rosen TE that was designed to show that quantum theory is incomplete. Although I agree that familiar objects of every-day experience do not seem to play a decisive role in this TE, I am wondering whether this tells us more about quantum mechanics than about TEs. After all, it is remarkable that the Einstein–Podolsky–Rosen TE is one of the few TEs in quantum mechanics in which quantum phenomena are not modeled onto every-day scenarios (like, for instance, in Schrödinger’s cat), but in which the quantum phenomena themselves are the objects of TE reasoning. However, since discussing this issue would lead me too far afield, all I can do here is to refer the reader to more detailed studies such as, e.g., McAllister ( 1996 , pp. 248–250), Van Dyck ( 2003 ) or Peacock ( 2018 ).

9 What I have in mind here is this: In part, the didactic value of TEs stems from the fact that they provide us with exemplary scenarios in which the application of abstract concepts becomes experienceable in an intuitive, quasi-sensory and oftentimes first-personal manner. After having imagined myself in two different places within the same imaginary scenario, the outcome of the train TE becomes directly observable without the need for any kind of higher-order cognitive skills such as mathematical abilities. But, of course, it is possible to achieve similar results by relying on imaginary scenarios with higher degrees of abstractness. For example, trains, wave-like light flashes and embodied observers could be replaced by rigid rods, ideal clocks and detection devices. These could then be replaced by systems of coordinates, which in turn could be replaced by equations that govern the transformations between frames quantitatively. On my view, such an “ascent from embodied sensation” (Gooding 1992 , p. 294) to increasingly abstract systems of representation is a very effective way to make the physical meaning of mathematical concepts and techniques intelligible (cf., also, Giere 1988 ; Nersessian 2005 ).

10 One reviewer has wondered whether the kind of manipulationism I am advocating would be improved by replacing all references to mental representations with concepts, thus reducing “ S understands P ” to “ S possesses the concepts needed to make relevant inferences about P ”. Although much more would have to be said about this complex issue (cf., e.g., Machery 2009 ; Margolis and Laurence 2011 ), my response is twofold: Whether a manipulationist account would benefit from replacing mental representations with concepts depends, of course, on what one takes concepts to be. While there is little agreement among philosophers, it seems very common among psychologists to “refer to a concept as a mental representation that is used to meet a variety of cognitive functions” (Solomon et al. 1999 , p. 100). Following psychologists on this not only seems to be the scientifically less controversial move. It also makes mental representation the more general term, allowing for the possibility that we sometimes understand by means of one kind of mental representation (concepts) and sometimes by means of others (e.g. imaginary scenarios). Concerning the issue of concept possession, I agree that a good account of understanding should also be an account of concept possession, and that one of the primary aims of TEs is to bring concepts under one’s cognitive control. However, and this is particularly important in philosophy of science, a distinction must be made between merely and genuinely possessing a concept. While knowing textbook definitions might be sufficient for the former, genuine possession of a concept like “reference frame” requires the ability to use it. Hence, although concept possession is important, manipulation is, in my view, more fundamental.

11 The phenomenon of time dilation seems to give rise to several paradoxical consequences, the “twin paradox” being the most famous one. Imagine two identical twins, one of whom travels through space at 0.999 c for one earth-year, while the other stays on earth. Since, according to the principle of relativity, there is no privileged frame of reference, each twin could be described to move away from the other at a velocity close to c . If this were the case, this would lead to the paradoxical consequence that, upon their reunion, each twin should find the other to have aged significantly less. However, the problem with this way of looking at things is that the spacetime paths of the two twins are in fact asymmetrical. Since the traveling twin must turn around in order to come back to earth, her trajectory involves at least two inertial frames and several accelerations and decelerations. Cf., for more details, e.g. Luminet ( 2010 ).

12 It should be added that the time dilation effects are further magnified by the fact that soldiers spend much of their traveling time in cryogenic deepfreeze.

13 As one reviewer has pointed out, notions such as “existential feeling” or “existential understanding” could be taken to allude to the works of thinkers that are commonly associated with Existentialism. Even though I agree that it would be worthwhile to contrast my manipulationist account with, for instance, Heidegger’s conception of understanding (cf., e.g. Wrathall 2013 ), or to expand my discussion of existential understanding by Heidegger’s or Merleau-Ponty’s “existential conception of science” (cf., e.g., Rouse 1986 ), doing so would require much more space than I have here.

14 Haldeman ignores several factors that currently stand in the way of making interstellar travel a reality. Besides the fact that the available methods of spaceship propulsion do not provide nearly enough kinetic energy to reach velocities close to c , factors such as the presence of high-energy, ionizing cosmic ray nuclei present serious challenges for ensuring the health of human space travelers (cf., e.g., Setlow 2003 ).

15 This, of course, is not to say that relativistic effects aren’t already interfering with our lifeworld. For instance, since clocks on satellites are affected by their high speeds, global navigation systems would not deliver sufficiently accurate results if time dilation was ignored.

16 Even tough I believe that inner-theoretical clarification is the most common achievement of TEs in science, one might, for example, point to Stevin’s chain as a TE that produces rather than clarifies a theory.

17 One could wonder whether it is really possible to understand how SR affects the emotional and social dimensions of human existence without also understanding how time dilation comes about. On my view, this is indeed possible: In order to gain existential understanding of SR, a cognitive agent only needs to have factual knowledge that time dilation exists, that it occurs at speeds close to c and that it interferes with the aging processes of subjects in different frames. Although physical understanding of time dilation might be a bonus, it is not necessary in order to understand how existential feelings such as alienation would be amplified by being de-synced from the rest of humanity.

18 Science fiction that is rigorous in its use of scientific theories is commonly referred to as “hard” science fiction. It should be apparent that my argument only applies to this sub-genre and not to more fantastic variants of science fiction.

19 Data is a human-like, self-conscious android with exceptional computational capabilities, but without the ability to experience emotions of any kind.

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Fiction as Thought Experiment

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Catherine Z. Elgin; Fiction as Thought Experiment. Perspectives on Science 2014; 22 (2): 221–241. doi: https://doi.org/10.1162/POSC_a_00128

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Although fictions and thought experiments are not physical realizations of the phenomena they pertain to, like real experiments, they exemplify properties or patterns that they share with those phenomena. They thereby afford epistemic access to properties and patterns that are realized in fact.

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The Forever War: understanding, science fiction, and thought experiments

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• 1 Department for Culture and Communication, Linköping University, 581 83 Linköping, Sweden.
• PMID: 34720221
• PMCID: PMC8550122
• DOI: 10.1007/s11229-019-02306-6

The aim of this paper is to show that scientific thought experiments and works of science fiction are highly suitable tools for facilitating and increasing understanding of science. After comparing one of Einstein's most famous thought experiments with the science fiction novel "The Forever War", I shall argue that both proceed similarly in making some of the more outlandish consequences of special relativity theory intelligible. However, as I will also point out, understanding in thought experiments and understanding in science fiction differ in one important respect: While the former aim at what I shall call "physical understanding", science fiction novels typically have "existential understanding" as their target.

Keywords: Science fiction; Thought experiments; Understanding.

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Science Fiction and Philosophy

Philosopher Susan Schneider's new book examines age-old philosophical puzzles through the lens of science fiction.

Imagine you inhabit a world, three centuries from now, in which advances in biology and technology allow human beings to ‘upgrade’ their brains to become superintelligent beings. You choose to resist these neural enhancements, but you are conflicted about your decision. You cannot understand the thoughts of enhanced humans without undergoing the upgrades yourself, but you are also plagued by the possibility that their way of thinking could be flawed.

Susan Schneider, Assistant Professor of Philosophy, poses this conundrum in the introduction to her new edited volume, Science Fiction and Philosophy . She writes, “Is there some sort of neutral vantage point or at least a set of plausible principles with which to guide you in framing a response to such a challenge?” The scenario is one of many presented by the readings in Schneider’s book that challenge readers to engage in thought experiments—hypothetical situations that often exceed the bounds of physical reality but can be philosophically enlightening.

Many of the philosophical questions addressed in Science Fiction and Philosophy are age-old—the nature of knowledge, of the external world, of personhood—but they are approached through thought experiments borrowed from the world of science fiction. Schneider believes that the perspectives science fiction brings to bear on philosophical questions grow increasingly relevant as advances in areas like neuroscience and technology add to and complicate our knowledge of ourselves and the world around us.

“What is the nature of the mind if the physical brain extends to encompass things we don’t traditionally think of as part of our brain but become seamlessly interwoven with us?” - Susan Schneider

“As cognitive science began to develop,” she says, “a lot of science fiction seemed to veer into science fact with respect to the brain. The same is true in physics—physicists talk about time travel in the context of relativity theory for example. It’s interesting to consider these issues in the context of science fiction thought experiments that also provoke thought about where the future is going.”

To examine the reality of the external world, for example, Science Fiction and Philosophy offers not only Plato’s Allegory of the Cave, but also an essay by David Chalmers about the science fiction blockbuster The Matrix . Ideas of free will and the nature of persons are considered in the context of the Computational Theory of Mind (CTM)—the proposition, based in cognitive science, that one’s mind is essentially a program running on the hardware of the brain. The book also explores artificial intelligence, the nature of space and time, and the new ethical and political questions generated by our changing understanding of these issues.

In her own essay for the book, “ Mindscan : Transcending and Enhancing the Human Brain,” Schneider draws from her work in the philosophy of mind, which explores how the mind relates to the world that science uncovers. She considers whether CTM supports the case for radical human enhancement through technology.

“Suppose that one day we can have working memory enhancements or artificial connections to the internet inserted in our retinas,” Schneider speculates. “What is the nature of the mind if the physical brain extends to encompass things we don’t traditionally think of as part of our brain but become seamlessly interwoven with us?” These up and coming realities, Schneider explains, seem to favor CTM, which proposes that individuals are informational patterns and that the medium—artificial or organic—on which these patterns are instantiated does not play a part in defining personhood.

Schneider’s essay interrogates the plausibility of this theory by using, as a thought experiment, Robert Sawyer’s science fiction novel Mindscan . She ponders questions such as, if persons are patterns, might enhancements that cause radical shifts to these patterns be tantamount to suicide? Or, if people’s patterns are duplicated and uploaded onto artificial brains, such as that of an android, how do they remain individuals, unique and separate from their replications?

Schneider believes that a synthesis between cognitive science and philosophy is necessary to achieve an understanding of the mind that is complete enough to address such quandaries. “My own view on the nature of personhood and mind is that the conception put forth by cognitive science needs a lot of philosophical work,” she says, “and I’m reworking the philosophical commitments of CTM to address what I see as some of the problems.”

At Penn, Schneider is a member of the Center for Cognitive Neuroscience, the Institute for Research in Cognitive Science, and the newly established Center for Neuroscience and Society, which plays an important role in facilitating cross-disciplinary research that addresses the impact neuroscience makes on society.

“The new center,” Schneider says, “will be an important venue for interdisciplinary debates on what neuroscience says about timeless philosophical questions concerning the nature of persons and their minds, and relatedly, whether we should enhance our mental lives via neurotechnologies. It’s extraordinarily important to think now about these issues because scientific innovations and discoveries concerning the brain and artificial intelligence exponentially increase and complicate the ethical questions that we will face in the future.”

By Priya Ratneshwar

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Thought Experiments

Thought experiments are basically devices of the imagination. They are employed for various purposes such an entertainment, education, conceptual analysis, exploration, hypothesizing, theory selection, theory implementation, etc. Some applications are more controversial than others. Few would object to thought experiments that serve to illustrate complex states of affairs, or those that are used in educational contexts. The situation is different, however, with respect to the appropriation of imagined scenarios to investigate reality (very broadly conceived to include things like electrons, tables, rain, beliefs, morals, people, numbers, universes, and even divine beings). It is this use of thought experiments that attracts most of the attention inside and outside of philosophical discourse. Significant is the overlap here with many other central philosophical topics, such as the nature of the imagination, the importance of understanding in contrast to explanation, the role of intuition in human cognition, and the relationship between fiction and truth. Moreover, thought experiments are interdisciplinary in two important respects. Firstly, not only philosophers study them as a research topic, but also historians, cognitive scientists, psychologists, etc. Secondly, they are used in many disciplines, including biology, economics, history, mathematics, philosophy, and physics (although, interestingly, not with the same frequency in each).

Most often thought experiments are communicated in narrative form, frequently with diagrams. It is important to distinguish between the imagined scenarios that are featured in thought experiments, on the one hand, and the narratives that establish those scenarios in people’s mind, on the other. Once a scenario is imagined it may assume a life on its own, and this explains partly the creative power of a good thought experiment. Experimental results may obtain that actually run counter to the narrative that initiated the discussion of an imagined scenario. Besides, thought experiments should be distinguished from thinking about experiments, from merely imagining any experiments to be conducted outside the imagination, and from psychological experiments with thoughts, though there may be some overlap. They should also be distinguished from counterfactual reasoning in general, as they seem to require a palpable element, which explains the impression that something is experienced in a thought experiment (i.e., being seen, felt, heard, etc.; not literally, of course). In other words, though many call any counterfactual or hypothetical situation a thought experiment (see, e.g., Rescher 1991), this appears too encompassing.

It is a quite different matter as to whether there is a logical structure common to all of thought experiments. Based on such considerations of logical structure, a taxonomy has been proposed according to which all thought experiments fall into two classes: “Necessity Refuters” and “Possibility Refuters” (see Sorensen 1992, 132–160). Such proposals especially fuel the debate about identity conditions of thought experiments. What modifications to logical structure does a thought experiment tolerate before it ceases to exist and a new one is born? In other words, how much emphasis on propositional characteristics is appropriate in the analysis of thought experiments?

Looking at the development of the discussion about thought experiments over the past thirty years, it is fair to say that thought experiments were primarily an important topic in the philosophy of science and the philosophy of philosophy (“metaphilosophy”), before the scope widened up at a later point. There is a simple reason for that path. At the core of the discussion sits a relatively simple epistemological challenge that is presented in a particularly powerful manner by numerous thought experiments that the history of science has to offer. They suggest that we can learn about the real world by virtue of merely thinking about imagined scenarios. But how can we learn about reality (if we can at all), just by thinking? This is the central question. Are there really thought experiments that enable us to acquire new knowledge about nature without new empirical data? If so, where does the new information come from, assuming that it takes new information to learn anything new about the world by means of thought experiments? Finally, how can we distinguish good from bad instances of thought experiments? These questions seem urgent with respect to scientific thought experiments, because many “recognize them as an occasionally potent tool for increasing our understanding of nature” (Kuhn 1977, p. 241). “Historically their role is very close to the double one played by actual laboratory experiments and observations. First, thought experiments can disclose nature’s failure to conform to a previously held set of expectations. Second, they can suggest particular ways in which both expectation and theory must henceforth be revised” (Kuhn 1977, p. 261). Yet, questions surrounding the epistemological challenge that certain scientific thought experiments pose, are equally urgent with respect to thought experiments outside of the natural sciences. This is especially true with respect to philosophy itself. Philosophy offers numerous examples of thought experiments that play a role similar in importance to some scientific thought experiments. And this fact provokes in turn further inquiries into the relationship between the natural sciences and philosophy, especially with respect to phenomena that implicate both the natural sciences and philosophy, such as the mind and free will (see, e.g., Wilkes 1988; Young 2013).

If scientific practice has room for thought experiments, then the question arises as to why we would want philosophical methodology to be more discriminatory in this respect. One reason that is often offered is that results of scientific thought experiments may be subjected to further empirical testing. Obviously, this can’t be done for philosophical thought experiments. But, it seems difficult to accept a categorical separation of science and philosophy along these lines. The 17th century saw some of the most brilliant practitioners of thought experimentation in Galileo, Descartes, Newton, and Leibniz, all of whom pursued the project of “natural philosophy.” And in our own time, the creation of quantum mechanics and relativity are almost unthinkable without the crucial role played by thought experiments, most of which relate to important philosophical issues that arise from these scientific theories. Besides, much of ethics, philosophy of language, and philosophy of mind is based on the results of thought experiments in a way that seems very similar to scientific thought experiments (though some might contest this), including Searle’s Chinese room, Putnam’s twin earth, and Jackson’s Mary the colour scientist. Philosophy, even more than the sciences, would be severely impoverished without thought experiments. These observations partly explain why it has been argued that a more “unified” account of thought experiments is desirable (see Boniolo 1997; Cooper 2005, pp. 329–330; Gähde 2000). Of course, it is important not to downplay the significant differences between the sciences and philosophy. But an account of thought experiments seems more powerful if it can do justice to the fact that not only in the sciences we find many of them.

There have been several attempts to define “thought experiment” along the lines of traditional conceptual analysis (see, e.g., Picha 2011; McComb 2013), but likely it will be better to leave the term loosely characterized, so as not to prejudice the ongoing investigation. Of course, we need to have some idea as to what thought experiments are to guide a proper philosophical analysis (see Häggqvist 2009), but this does not mean that we need to begin with a technical definition, specifying necessary and sufficient conditions. In fact, many of the most important concepts we deal with remain rather loosely defined when philosophical inquiry begins, e.g., religion or democracy. Luckily, there are plenty of examples to refer to in order to circumscribe our subject matter well enough. As well as those already mentioned, there are Newton’s bucket, Heisenberg’s gamma-ray microscope, Einstein’s elevator, Leibniz’s mill, Parfit’s people who split like amoebas, and Thomson’s violinist. Everyone is probably familiar with some of these. Less familiar thought experiments include the mouse that breaks into the tabernacle of a medieval Roman Catholic Church building to feed on the consecrated wafers kept in there (see Fehige 2018). Roman Catholic Christians believe that a consecrated wafer is the “body of Christ”. The “substance” of the wafer, understood in terms of Aristotelian categories, is believed to be replaced. In its place is the “substance” of Christ’s body after consecration by a priest. Only the Aristotelian “accidents” of the wafer remain intact (smell, colour, texture, etc.). Does the mouse eat the “body of Christ” (if any human actually does)? If not, then the “body of Christ” seems to be less than an objective reality; if yes, the “body of Christ” must be able to do good in the absence of a believing human soul. Another example less known is “the dome” thought experiment, which is to prove indeterminism in Newtonian physics. Imagine a mass sitting on a radially symmetric surface in a gravitational field. Guided by Newton’s laws of motion one comes to realize that the mass can either remain at rest for all times, or spontaneously move in an arbitrary direction (see Norton 2008). This thought experiment triggers a number of very interesting questions concerning the nature of Newtonian theory, the meaning of “physical”, and the role of idealizations in physics. And, of course, does it show what it claims? (see Malament 2008).

This entry continues with an overview of the characteristics of thought experiments in light of examples in Section 1. Section 2 reviews several taxonomies for classfying thought experiments and Section 3 sketches a history of philosophical inquiry into the nature of thought experiments. Section 4 covers several views representing the current state of the debate. The entry concludes by highlighting some trends in discussions surrounding the so-called laboratory of the mind.

1. Important Characteristics of Thought Experiments

2. taxonomies of thought experiments, 3. the history of thought experiments, 4.1 the skeptical objection, 4.2 the intuition–based account, 4.3 the argument view, 4.4 conceptual constructivism, 4.5 experimentalism, 4.6 the mental–model account, 5. going forward, other internet resources, related entries.

Theorizing about thought experiments usually turns on the details or the patterns of specific cases. Familiarity with a wide range of examples is crucial for commentators, and the list is very long (see, e.g., Stuart et al. 2018, pp. 558–560) We will provide a few here. One of the most beautiful early instances (found in Lucretius, De Rerum Natura 1.951–987; see Bailey 1950, pp. 58–59) attempts to show that space is infinite: if there is a purported boundary to the universe, we can toss a spear at it. If the spear flies through, it isn’t a boundary after all; if the spear bounces back, then there must be something beyond the supposed edge of space, a cosmic wall that stopped the spear, a wall that is itself in space. Either way, there is no edge of the universe; thus, space must be infinite.

This example nicely illustrates many of the most common features of what it means to engage in the conduct of thought experiments: we visualize some situation that we have set up in the imagination; we let it run or we carry out an operation; we see what happens; finally, we draw a conclusion. The example also illustrates the fallibility of thought experiments. Since the time of Lucretius, we’ve learned how to conceptualize space so that it could be both finite and unbounded. Imagine a circle, which is a one-dimensional space. As we move around, there is no edge, but it is nevertheless finite. The universe might be a three-dimensional version of this topology. It is, therefore, true that we must try to be mindful of unexpected limitations due to “physical scale effects” (Klee 2008), or other such things, when imagining counterfactual scenarios.

Figure 1. “Welcome to the edge of the Universe”

Often a real experiment that is meant to be the analogue of a thought experiment is impossible to be carried out as such due to physical, technological, ethical, or financial limitations (see, e.g., Sorensen 1992, pp. 200–202); but physical unrealizability needn’t be a defining condition of thought experiments. Rather, the main point is that we seem able to get a grip on nature just by thinking, and therein lies the great interest for philosophy. That was the position of Ernst Mach (see Mach, 1897 and 1905; for a most instructive assessments of his views see Kühne 2006, pp. 165–202, and Sorensen 1992, pp. 51–75). Thought experiments are on a spectrum of different kinds of experiments. They allow us to tap into a great store of “instinctive knowledge” picked up from past experience. We will get back to Mach’s theory further down. His account of thought experiments remains one of the major theories of how thought experiments work. One of Mach’s favourite examples is due to Simon Stevin (see Mach, 1883, pp. 48–58). When a chain is draped over a double frictionless plane, as in Fig. 2a, how will it move? Add some links as in Fig. 2b. Now it is obvious. The initial setup must have been in static equilibrium. Otherwise, we would have a perpetual motion machine; and according to our experience-based “instinctive knowledge,” says Mach, this is impossible. We do not have to perform the experiment in the real world, which we could not do, anyway, since it would require a perfectly frictionless plane. Nevertheless the outcome seems compelling.

Figure 2. “How will it move?”

Judith Thomson provided one of the most striking and effective thought experiments in the moral realm (see Thomson 1971). Her example is aimed at a popular anti-abortion argument that goes something like this: A fetus is an innocent person. All innocent persons have a right to life. Abortion results in the death of a fetus. Therefore, abortion is morally wrong. In her thought experiment, Thomson asks you to imagine a famous violinist falling into a coma. The society of music lovers determines from medical records that you and you alone can save the violinist’s life by being hooked up to him for nine months. The music lovers break into your home while you are asleep and hook the unconscious (and unknowing, hence innocent) violinist to you. You may want to unhook him, but you are then faced with the following argument put forward by the music lovers: The violinist is an innocent person. All innocent persons have a right to life. Unhooking him will result in his death. Therefore, unhooking him is morally wrong. However, the argument, even though it has the same structure as the anti-abortion argument, does not seem convincing in this case. You would be very generous to remain attached for nine months, but you are not morally obligated to do so. The parallel with the abortion case is evident. Thomson’s thought experiment is effective in distinguishing two concepts that had previously been run together: “right to life” and “right to what is needed to sustain life.” The fetus and the violinist might each have the former, but it is not evident that either has the latter. The upshot is that even if the fetus has a right to life (which Thomson does not believe but allows for the sake of the argument), it may still be morally permissible to abort. Those opposed to Thomson’s view have two options. They can either dismiss her thought experiment as a useless fiction. In fact, thought experiments as a method in ethics have their critics (see, e.g., Dancy 1985). Alternatively, they can provide a different version of the same scenario to challenge the conclusion. It is a very intriguing feature of thought experiments that they can be “rethought” (see Bokulich 2001). Real experiments are frequently open to reinterpretation, too. In this respect there does not seem to be a principled difference between the two classes of experiments.

Like arguments, thought experiments can be criticized in different ways. Perhaps the set up is faulty; perhaps the conclusions drawn from the thought experiment are not justified. Similar criticisms can arise in real experiments. Counter thought experiments are perhaps another form of criticism. They do not target the premises or conclusions involved in a particular thought experiment but question the phenomenon, i.e. the non-propositional heart of an imagined scenario (see Brown 2007). For example, Daniel Dennett is convinced that Frank Jackson’s Mary thought experiment is poor evidence to oppose physicalism in philosophy of mind. In Jackson’s version, Mary, who knows everything physics and the neurosciences can possibly know about colours but grew up in a colourless environment (seeing only black, white and grey things), allegedly learns something new when she sees a red tomato for the first time. Now she knows what it is like to experience red. This is an argument for qualia as something over and above the physical. Instead of a red tomato, Dennett, in his version of the thought experiment, presents Mary with a bright blue banana. In his version of the story (which seems just as plausible as Jackson’s), Mary balks and says she is being tricked, since she knows that bananas are yellow, and this, says Mary, is a consequence of knowing everything physical about colour perception. Mary does not learn anything new when she sees coloured objects for the first time, so there is no case against physicalism after all. Jackson’s initial thought experiment was very persuasive, but Dennett’s seems equally so, thus, undermining Jackson’s argument, although there is greater resistence to the conclusion of the latter than the former! Dennett complains a great deal about the ongoing “Mariology”, as he calls the continuing acceptance of Jackson’s thought experiment as a poweful case against physicalism.

Clearly, thought experiments are characterized by an intriguing plasticity, and this raises the interesting question of what it is that preserves the identity of a thought experiment. Replacing a red tomato with a blue banana might still leave us with the same thought experiment––slightly revised. But, at what point do we get a new thought experiment? This is not merely a question about conceptual vagueness. It helps to facilitate a discussion of the intuitively most plausible view about the cognitive efficacy of thought experiments, according to which this power depends on their being arguments, in a fairly strict sense of argument. John D. Norton holds such a view, which will be discussed below. In light of cases where the discussion of one and the same thought experiment played an important role in settling a dispute, the following problem arises: how can one and the same thought experiment support opposing views about a particular matter if the arguments that correspond to the different versions of the thought experiment that were entertained by the disputing parties are significantly different? The dilemma is: we could say that if there is more than one argument then there is more than one thought experiment involved in the dispute. But if that is true then the disputing parties simply talked past each other. One party presented an argument that the other party ignored while presenting their own. Alternatively, we can say that one thought experiment can correspond to many different arguments. But, if that is true then it becomes unclear in what non-trivial sense thought experiments are supposed to be identical with arguments (see Bishop 1999, and the response by Norton 2004, 63–64).

The plasticity of thought experiments coheres with another feature of thought experiments, namely that they seem to have “evidential significance only historically and locally, i.e., when and where premises that attribute evidential significance to it […] are endorsed” (McAllister 1996, p. 248).

Many taxonomies can be found in the literature. They are not mutually exclusive. We will present three of them. The first follows the type of purpose thought experiments serve. A very rudimentary version of it can be found in Mach (1897 and 1905). Such a classification makes sense, because an “imaginary experiment should be judged on its specific purpose” (Krimsky 1973, p. 331). Thought experiments are conducted for diverse reasons (see, e.g., DeMay 2006; Sorensen 1992, pp. 7–15), and this in a variety of areas, including economics (see, e.g., Herfeld 2019; Thoma 2016), education (Helm and Gilbert 1985; Helm et al. 1985, Klassen 2006; Sriraman 2006; Stonier 1990), history (see, e.g., Maar 2014; Reiss 2009), literature (see, e.g., Davies 2007; Elgin 2004), mathematics (see, e.g. Brown 1991 [2011], pp. 90–97; Glas 1999), morality (see, e.g., Hauerwas 1996; Wilson 2016), as well as the natural sciences (see Krimsky 1973), the socio-political realm (see, e.g. Roberts 1993: Thaler 2016), and theology (see, e.g., Gregersen 2014; Fehige 2024). Thought experiments may be used to entertain. This is probably true of short stories or novels which some argue qualify as thought experiments if certain conditions apply (see, e.g., Davenport 1983). Some thought experiments fulfil a specific function within a theory (see Borsboom et al. 2002). Others are executed because it is impossible to run the experimental scenario in the real world (see, e.g., Sorensen 1992, pp. 200–202). Sometimes thought experiments help to illustrate and clarify very abstract states of affairs, thereby accelerating the process of understanding (see Behmel 2001). Again others serve as examples in conceptual analysis (see Cohnitz 2006). And, then there are those that matter in the process of theory discovery (Praem and Steglich–Peterson 2015). The thought experiments that have received most of the attention are taken to provide evidence for or against a theory, putting them on a par with real-world experiments (see, e.g., Gendler 2004). The different ways to use thought experiments, of course, do not exclude one another. Most obviously, for example, a thought experiment can both entertain and make a case against a theory.

A second taxonomy classifies thought experiments in terms of their logical structure (see Sorensen 1992, pp. 132–166). The idea is to divide all thought experiments into two types of “alethic refuters”: “Although there are a number of ways to classify thought experiments, a refutation format scores the most points when judged by familiarity, specificity, and simplicity. According to this scheme, thought experiments aim at overturning statements by disproving one of their modal consequences. Modalities are operators that are applied to propositions to yield new propositions. There are deontic modalities ( permissible, forbidden ), epistemic modalities ( know, believe ), and alethic modalities ( possible, necessary ). The alethic modalities are the best–known and more–basic modality. Hence, we won’t miss anything by concentrating on them” (Sorensen 1992, p. 135). One type of thought experiment “is designed to refute a statement by showing that something ruled out as impossible by that statement is really possible after all” (Sorensen 1992, p. 135). The most discussed examples in the metaphilosophical discussion on thought experiments is of such a type, namely the Gettier scenarios (see Grundmann & Horvarth 2014; Saint-Germier 2019). They are designed to refute the claim that all knowledge is justified, true belief. They serve as a “necessity refuter.” The other type collects examples of “possibility refuters”. They don’t affirm “the possibility of the thought experiment’s content”. Instead, they establish “copossibilities”. A wonderful example is the scenario of an omnipotent God who faces the task of creating a stone too heavy for that God to lift. It seems God cannot succeed. The notion of divine omnipotence causes some headache here.

A third taxonomy (see Brown 1991, chapter 2), which has not gone unchallenged (see Norton 1993b), is more limited than the first two insofar as it focuses largely on the class of those thought experiments that are taken to function in theory choice, which is the use of thought experiments that has been receiving most of the attention. According to this taxonomy, the main division is constructive vs. destructive and resembles Karl Popper’s distinction between apologetic and critical thought experiments. Popper actually distinguishes between three types of thought experiments: heuristic (to illustrate a theory), critical (against a theory) and apologetic (in favour of a theory) (see Popper 1959). His case in favour of a critical and against an apologetic use of thought experiments is very limited. He focuses exclusively on quantum physics and doesn’t really say much to address the primary epistemological challenge presented by the success of critical thought experiments.

Among destructive thought experiments , the following subtypes can be identified: the simplest of these is to draw out a contradiction in a theory, thereby refuting it. The first part of Galileo’s famous falling bodies example does this. It shows that in Aristotle’s account, a composite body (cannon ball and musket ball attached) would have to fall both faster and slower than the cannon ball alone. A second subtype is constituted by those thought experiments that aim to show that the theory in question is in conflict with other beliefs that we hold. Schrödinger’s well-known cat paradox, for instance, does not show that quantum theory (at least on some interpretations) is internally inconsistent (see Schrödinger 1935, p. 812; translation: Trimmer 1980, p. 328): “A cat is penned up in a steel chamber, along with the following diabolical device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of one hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The first atomic decay would have poisoned it. The q-function of the entire system would express this by having in it the living and the dead cat (pardon the expression) mixed or smeared out in equal parts.” This thought experiment shows that quantum theory (as interpreted by Bohr) is in conflict with some very powerful common sense beliefs we have about macro-sized objects such as cats––they cannot be both dead and alive in any sense whatsoever. The bizarreness of superpositions in the atomic world is worrisome enough, says Schrödinger, but when it implies that same bizarreness at an everyday level, it is intolerable. There is a third subtype of negative thought experiments, namely when, in effect, a central assumption or premise of the thought experiment itself is undermined. For example, as we have seen above, Thomson showed with her thought experiment that “right to life” and “right to what is needed to sustain life” had been run together. When distinguished, the argument against abortion is negatively affected.

A fourth sub-type of negative thought experiments are “counter thought experiments” (see Brown 2007). Norton very usefully introduces a related idea: “thought-experiment/anti-thought-experiment pairs” (see Norton 2004, pp. 45–49). Above, we have already encountered this subtype in our discussion of Lucretius’ spear-thought experiment, and with Dennett’s reply to Jackson’s much discussed Mary the colour scientist thought experiment. Here we would like to add one more example, namely Mach’s counter thought experiment against absolute space. In his Principia Mathematica , Newton offers a pair of thought experiments as evidence for absolute space. One is the bucket thought experiment with water climbing the wall (see Fig. 3), the other is about a pair of spheres joined by a cord that maintained its tension in otherwise empty space (see Fig. 4). The explanation for these phenomena, argues Newton, is absolute space: the bucket and the joined spheres are rotating with respect to space itself. In response, Mach modifies the scenario and argues, contra Newton, that the two spheres would move toward one another thanks to the tension in the cord, and if we rotated a very thick, massive ring around a stationary bucket, we would see the water climb the bucket wall. (For further discussion of Mach’s counter thought experiment to Newton’s see Kühne 2006, pp. 191–202). In short, the point of Mach’s counter thought experiments is to describe the phenomena of the thought experiments’ scenarios differently, that is, to declare that different things would happen. Mach’s counter thought experiment undermines our confidence in Newton’s thought experiments. Absolute space might be a plausible explanation of the phenomena in Newton’s thought experiments, but now, in light of Mach’s counter thought experiment, we’re not so sure of the phenomena itself and thus of the idea of absolute space.

Figure 3. Stages in the bucket experiment

Figure 4. Two spheres held by a cord in otherwise empty space

To be effective, counter thought experiments needn’t be very plausible at all. In a court of law a jury would convict provided guilt is established “beyond a reasonable doubt.” A common defence strategy is to provide an alternative account of the evidence that has just enough plausibility to put the prosecution’s case into some measure of doubt. That is sufficient to undermine it. A counter thought experiment need only do that much to be effective, and in this sense it operates like a “necessity refuter” in Sorensen’s sense.

In addition to destructive ones, there is a second type, the constructive thought experiments . Unsurprisingly, there are many ways they could provide positive support for a theory. One of these is to provide a kind of illustration that makes a theory’s claims clear and evident. In such cases thought experiments serve as a kind of heuristic aid. A result may already be well established, but the thought experiment can lead to a very satisfying sense of understanding. In his Principia Mathematica , Newton provides a wonderful example showing how the moon is kept in its orbit in just the same way as an object falls to the earth (see Ducheyne 2006, pp. 435–437). He illustrates this by means of a cannon shooting a cannon ball further and further (see Fig. 5). In the limit, the earth curves away as fast as the ball falls, with the eventual result being that the cannon ball will return to the spot where it was fired, and, if not impeded, will go around again and again. This is what the moon is doing. We could arrive at the same conclusion through calculation. But Newton’s thought experiment provides that elusive sense of understanding. It’s a wonderful example of the “aha effect” that is typical of many powerful thought experiments.

Figure 5. “The shot heard around the world”

Thomson’s violinist showed that abortion could be morally permissible even when the fetus has a right to life. Similarly, Einstein’s elevator showed that light will bend in a gravitational field, because according to the principle of equivalence, there is no difference between such a frame of reference and one that is accelerating in free space; the laws of physics are the same in all. Suppose then, an observer is inside an elevator sealed off from the outside so that the observer cannot tell whether he is in a gravitational field or accelerating. If it were accelerating, and if a light beam were to enter one side, then, due to the elevator’s motion, the beam would appear to drop or curve down as it crossed the elevator. Consequently, it would have to do the same thing if the elevator was in a gravitational field. Therefore, gravity ‘bends’ light.

Maxwell’s demon showed that entropy could be decreased: The second law of thermodynamics implies that heat won’t pass from a cold body to a hot one. In classical thermodynamics this law is quite strict; but in Maxwell’s kinetic theory of heat there is a probability, though extremely small, of such an event happening. Some thought this a reductio ad absurdum of Maxwell’s theory. To show how it is possible to violate the second law, Maxwell imagined a tiny creature who controls a door between two chambers. Fast molecules from the cold box are let into the hot box, and slow molecules from the hot are allowed into the cold. Thus, there will be an increase in the average speed in the hot box and a decrease in the average speed of molecules in the cold. Since, on Maxwell’s theory, heat is just the average speed of the molecules, there has been a flow of heat from a cold body to a hot one.

Parfit’s splitting persons shows that survival is a more important notion than identity when considering personhood (for a critical discussion see Gendler 2002a). We say they “show” such and such, but, “purport to show” might be better, since some of these thought experiments are quite contentious. What they have in common is that they aim to establish something positive. Unlike destructive thought experiments, they are not trying to demolish an existing theory, though they may do that in passing. To repeat an important point: in principle, given the fact that thought experiments can be rethought (see Bokulich 2001), and that the evidential significance is dependent on historical and local accomplishments (see McAllister 1996), it cannot be irrelevant to identify the intention of the thought experimenter, if one wants to determine the type of a thought experiment: “An imaginary experiment should be judged on its specific purpose” (Krimsky 1973, p. 331).

The practice of thought experiments is not an invention of modern science. That fact may be obscured by the dominance of scientific examples in the lively discussions about thouht experiments today. The Pre-Socratics “invented thought experimentation as a cognitive procedure and practiced it with great dedication and versatility” (Rescher 2005, p. 2). “There is no ancient Greek term corresponding to what we nowadays refer to as a thought experiment, and presumably ancient philosophers did not have our modern notion of a thought experiment. But there is no doubt that they did use thought experiments. In fact, they often employed them in ways similar to those of contemporary philosophers, that is, both for defending their own theories as well as for refuting the theories of their opponents ” (Ierodiakonou 2018, p. 31). (See also Becker 2018; Diamond 2002, pp. 229–232; Fuhrer 2009; Glas 1999; Ierodiakonou 2005; Ierodiakonou and Roux (eds.) 2011; Irvine 1991; Rescher 1991 and 2005, pp. 61–72). The situation is similar with respect to medieval natural philosophy, although there are further nuances to be considered (see King 1991). According to Edward Grant, during the late Middle Ages “the imagination became a formidable instrument in natural philosophy and theology in ways that would have astonished ancient Greek natural philosophers, especially Aristotle” (Grant 2007, p. 201). But this doesn’t mean that we have reason to think of Aristotle as an opponent of the conduct of thought experiments tout court . On the contrary, “Aristotle uses thought experiments for argumentative persuasion and in places where, due to the obscure nature of the subject matter or the counterintuitive nature of the thesis they are meant to support, insight cannot be readily communicated by appeal to observational facts” (Corcilius 2018, p. 73). With a few exceptions that involved problems of motion, “the scholastics” of the medieval period made no meaningful effort to transform their hypothetical conclusions into specific knowledge about the physical world. They did, however, assume that although these hypothetical conclusions were naturally impossible, God could produce them supernaturally if he wished. Special attention received also a class of medieval thought experiments that does not rely on counterfactuals but depends on theological assumptions to study matters non-theological, namely those thought experiments involving angels, whose existence were affirmed at that time (see Perler 2008). Angels are gone by now (see Clark 1992), but not thought experiments. While most thought experiments involving angels have Christianity as their context, there is evidence of the practice of thought experiments also in the context of Islam and Judaism (see McGinnis 2018; Fisch 2019). In fact, the case has been made “that Ibn Sina is the first philosopher in the Aristotelian tradition, and thus perhaps the first in Western philosophy overall, to try to identify the psychological processes that go into postulating a hypothetical scenario. Ibn Sina also exhibits an interest in accounting for why, and to what extent, such psychological acts are thought to carry weight in our study of nature” (Kukkonen 2014, p. 434).

Ernst Mach is commonly credited with introducing the word “thought experiment” ( Gadankenexperiment ) and thereby coining a term for philosophical discussion (recently done, for instance, by Krauthausen 2015, p. 15). “ This view is incorrect, however! […] it can be substantiated that it was used […] already in 1811” (Witt-Hansen 1976, p. 48; see also Buzzoni 2008, pp. 14–15; 61–65; Kühne 2005, pp. 92–224; Moue et al. 2006, p. 63). The conceptual history of “thought experiment” goes back at least to the Danish “Tankeexperiment,” as it was used by Hans-Christian Ørsted. We can go back even further and find in the work of the German philosopher-scientist Georg Lichtenberg (1742–1799) a tacit theory of “experiments with thoughts and ideas.” These experiments help to overcome habits of thought that can inhibit scientific progress, and make possible an enlightened philosophy (see Schildknecht 1990, pp. 21; 123–169; Schöne 1982). Lichtenberg’s “aphoristic experiments” (see Stern 1963, pp. 112–126) reflect “that Lichtenberg’s scientific preoccupations are the formal and thematic prolegomena to his work as a literary artist” (Stern 1963, p. 126). Lichtenberg’s reflections on thought experimentation resemble those of Popper and Thomas S. Kuhn, and it is plausible to think of him as one important figure of the very first period in the history of philosophical inquiry into thought experiments (see Fehige and Stuart 2014).

Accordingly, the modern history of the philosophical investigation into thought experiments can be divided into four stages: in the 18th and 19th century the awareness of the importance of thought experiments in philosophy and science emerges. In addition to Lichtenberg and Hans-Christian Ørsted, special mention should be made of Novalis (see Daiber 2001). The topic reemerges in a more systematic manner at the beginning of the 20th century with little relation to the attempts made at the first stage. The stakeholders of the second stage were Pierre Duhem, Mach, and Alexius Meinong (see Duhem 1913, pp. 304–311; Mach, 1883, pp. 48–58, 1897 and 1905; Meinong 1907). A third stage, probably due to the rediscovery of the importance of scientific practice for a proper understanding of science, followed in the first part of the second half of the 20th century. Again, the contributions of this stage bear little relation to the two previous stages. While the third period has seen a number of noteworthy contributions (Cole 1983; Dancy 1985; Dennett 1985; Fodor 1964; Helm and Gilbert 1985; Helm et al. 1985; Krimsky 1973; McMullin 1985; Myers 1986; Poser 1984; Prudovsky 1989; Rehder 1980a,b; Yourgrau 1962 and 1967), the protagonists of this period were Alexandre Koyré, Kuhn and Popper. The ongoing philosophical exploration of thought experiments began in the 1980s, and marks the fourth stage. Arguably, it has been the most prolific one of all four stages. With some very important sign-postings in place (Horowitz and Massey (eds.) 1991; Sorensen 1992; Wilkes 1988), the ongoing discussion took off in light of a debate between James Robert Brown and John D. Norton (see for a concise statement of each position Brown 2004 and Norton 2004), which many have found useful to establish a contrast with their own alternative accounts of thought experiments. These views “represent the extremes of platonic rationalism and classic empiricism, respectively” (Moue et al. 2006, p. 69). They will be described below.

4. Current Views on Thought Experiments

At this point it is important to recall the key epistemological challenge described in the introduction: how can we learn about the real world through merely thinking about imagined scenarios? This challenge sits at the center of the discussion about thought experiments even though we must note that not all of the work discussed below focuses on it directly. Still, this section describes six views that can be seen as responding in some way to this challenge: The Skeptical Objection, The Intuition-Based Account, The Argument View, Conceptual Constructivism, Experimentalism, and The Mental-Model Account.

Of course, particular thought experiments have been contested. But for the most part, the practice of thought experiments in the sciences has been cheerfully accepted. Pierre Duhem, the great historian of physics, is almost alone in what has been understood as an outright condemnation of scientific thought experiments (see Duhem 1913, pp. 304–311). A thought experiment is no substitute for a real experiment, he claimed, and should be forbidden in science, including science education. However, in view of the important role of actual thought experiments in the history of physics — from Galileo’s falling bodies, to Newton’s bucket, to Einstein’s elevator — it is unlikely that anyone will feel or should feel much sympathy for Duhem’s strictures. We hasten to add that Buzzoni (2018) questions the validity of this reading of Duhem, and argues that already Mach’s reception of Duhem’s views suggests a more nuanced reading of Duhem’s position.

Philosophers can be as critical as Duhem when it comes to thought experimenting in their own field (see Peijnenburg; Atkinson 2003; Thagard 2014; Wilson 2016). At least thought experiments in science, the skeptic claims, can be tested by physical experiment. However, this is clearly false, since frictionless planes and universes empty of all material bodies cannot be produced in any laboratory. True, the results of philosophical thought experiments cannot be even approximately tested. But, skeptics say little about why thought experiments enjoy such popularity in philosophy. We are inclined to say that skeptics underestimate the importance of thought experiments for the creative mind in any field. Also, one mustn’t forget that the cognitive power of real world experiments isn’t a self-evident matter either.

Few are outright skeptics, however. Many take a more ambiguous stance. Sören Häggqvist, for example, has developed a normative model for philosophical thought experiments (see Häggqvist 1996 and 2009). Surprisingly, none of the commonly accepted philosophical thought experiments satisfies his model. And the process of identifying successful thought experiments is only the first step in addressing the central epistemological challenge posed by thought experiments. It gets much messier once we begin to ask exactly how reliable “successful” thought experiments are. Granted, there is some justice in worrying about the reliability of philosophical thought experiments (see, e.g., Klee 2008). This might be true for ethics (see Dancy 1985, Jackson 1992; Wilson 2016), conceptual analysis (see Fodor 1964), and the philosophy of mind: “A popular strategy in philosophy is to construct a certain sort of thought experiment I call intuition pump. […] Intuition pumps are often abused, though seldom deliberately” (Dennett 1985, p. 12). The claim by Dennett and others is that thought experiments too often rest on prejudice and faulty common sense; they are inherently conservative, while real science will likely result in highly-counterintuitive outcomes. Dennett believes that thought experiments rest on naive “folk concepts,” which is why they can be so misguided. It is far from clear that this is a fair charge. Everything involved in Galileo’s thought experiment that produced the principle of relativity could be called “folk concepts.” If we are inside a ship and perform a number of experiments, such as walking about, tossing a ball, watching birds fly about, we could not tell whether we are at rest in port or sailing over a smooth sea. The upshot is that nature behaves the same either way; the laws of nature are the same in any inertial frame. This result is profound and is still with us in Einstein’s relativity, whether it is folk physics or not.

Frequently discussed is the skeptical challenge raised by Kathleen Wilkes. She expresses a deep suspicion of scenarios such as Derek Parfit’s people splitting like an amoeba (see Parfit 1987; Gendler 2002a). Wilkes wants philosophy “to use science fact rather than science fiction or fantasy” (Wilkes 1988, p. 1), and therefore to refrain from using thought experiments because they are “both problematic and positively misleading” (Wilkes 1988, p. 2). She claims that thought experiments about personal identity in particular often fail to provide the background conditions against which the experiment is set (see Wilkes 1988, p. 7). She thinks we would not know what to say if we encountered someone who split like an amoeba. She insists that a legitimate thought experiment must not violate the known laws of nature. We do agree with Wilkes that underdetermination can be a problem. But instead of dismissing thought experiments in philosophy we should consider it a crucial factor in assessing the quality of a thought experiment (see Rescher 2005, pp. 9–14). That is to say that the more detailed the imaginary scenario in the relevant aspects is, the better the thought experiment (see Brendel 2004, pp. 97–99; Häggqvist 1996, p. 28).

We also agree that the inferences drawn in thought experimenting are highly problematic if the hypothetical scenario “is inadequately described” (Wilkes 1988, p. 8). But Wilkes seems to think that the lack of description is unavoidable, which supposedly amounts to a reason against philosophical thought experiments on personal identity because persons are not natural kinds. This makes it impossible to fill in necessary information to make the thought experiment work given its unavoidable underdetermination. Wilkes thinks that “whenever we are examining the ranges of concepts that do not pick on natural kinds, the problem of deciding what is or what is not ‘relevant’ to the success of the thought experiment is yet more problematic than the same question as it arises in science; and, unlike the scientific problem, it may not even have an answer in principle” (Wilkes 1988, p. 15). She adds that scientific laws — especially those describing biological kinds like human beings — “are not disjoint and independent, detachable from one another […]. They are interrelated, to varying degrees of course” (Wilkes 1988, p. 29). This implies, for example, that “a full psychophysiological account of the processes of human perception must at some stage link up with part at least of linguistic ability; for we typically see things under a certain description, and that description may be a very sophisticated one” (Wilkes 1988, p. 29). These considerations have her rule out experiments that challenge the human monopoly of personhood. No thought experiment, claims Wilkes, is well conceived if it involves non-human animals or computers as persons. But also those thought experiments can be ruled out which involve the “fission or fusion of humans” because it is not theoretically possible. “The total impact of the sum of laws that group us together as human beings (a natural kind category) precludes our splitting into two […] or fusing with someone else” (Wilkes 1988, p. 36).

One can ascertain here all too well the inherent difficulties in thinking about personal identity and the limited benefit some thought experiments might have for what is deemed the proper metaphysics of personal identity. Nevertheless, good reasons have been given in favour of the use of thought experiments about personal identity (see Beck 2006; Kolak 1993; Hershenov 2008). We also feel that the problems about thought experiments on personal identity reveal more about the intricate nature of the subject than about the usefulness of philosophical thought experiments. And, disregarding other shortcomings in Wilkes’ skepticism (for further discussion of Wilkes’ views see Beck 1992; Brooks 1994; Focquaert 2003; Häggqvist 1996, pp. 27–34), her suggestion that thought experimental scenarios would have to satisfy current scientific knowledge about the relevant entities featured in a thought experiment is highly implausible. We learn a great deal about the world and our theories when we wonder, for instance, what would have happened after the big bang if the law of gravity had been an inverse cube law instead of an inverse square. Would stars have failed to form? Reasoning about such a scenario is perfectly coherent and very instructive, even though it violates a law of nature.

To some extent we should share Wilkes’s concern that thought experimenting seems to be constrained only by relevant logical impossibilities and what seems intuitively acceptable. This is indeed problematic because intuitions can be highly misleading and relevant logical impossibilities are fairly ungrounded if they cannot be supplemented by relevant theoretical impossibilities based on current science in order to avoid the jump into futile fantasy. But in order to dismiss thought experimenting as a useful philosophical tool one has to show that intuition cannot be a source of knowledge and that an epistemic tool should be useless because there is a serious chance it can fail. Timothy Williamson has argued that we should forget about intuition as a cushion in the philosophical armchair (see Williamson 2004a,b, 2008, pp. 179–207, and 2009; see also Schaffer 2017). The importance of intuitions in philosophy has been neglected in the past (see Williamson 2004b, p. 109–110), and for too long intuition didn’t receive the attention it deserves (see, e.g., DePaul and Ramsey (eds.) 1998). Besides the traditional divide between empiricists, rationalists and skeptics, it is not only a very non-uniform use of the word “intuition” that makes it difficult to assess the progress of the last years of philosophical inquiry about intuitions. The situation has been complicated by the contributions of experimental philosophers on intuitions who add different reasons to question their reliability (see for a careful critique of those reasons: Ludwig 2007; see also Ludwig 2018). Generally speaking, the reliability of intuitions has been challenged on two grounds. One stems from an evolutionary explanation of the capacity to intuit; another is due to experiments which supposedly show the cultural relativity or racial and gender sensitivity of intuitions (see, e.g., Buckwalter and Stich 2010): “…a substantial list of philosophical intuitions vary across demographic groups and…they are influenced by a number of prima facie irrelevant factors…Some writers…have urged that these findings justify a thoroughgoing skepticism about the use of intuitions as evidence in philosophy…But we think this conclusion is much too strong…” (Stich & Toba 2018, p. 379). After all, knowledge without intuitions (if only common sense assumptions) seems impossible.

The recent discussion of intuitions in epistemology has barely made an impact on philosophical reflections about thought experiments. As far as philosophical thought experiments are concerned, this is as it should be, according to Williamson. In this respect George Bealer can be cited in support of Williamson, because for Bealer the talk about philosophical thought experiments reveals a conceptual confusion. Philosophy, he claims, is about “rational intuitions” and thought experiments can be only about “physical intuitions” (see Bealer 1998, pp. 207–208, and 2002, p. 74). To many, this is an implausible claim based on a deeply problematic “phenomenology of intuitions” resulting in a strict separation of “rational intuitions” from “physical intuitions”, on such grounds as an alleged immutability of “rational intuitions”. There are good reasons to believe that thought experiments appeal to intuitions in order to give us new insights about different realms of investigation, including philosophy. This kind of positive connection is what Williamson has in mind when addressing the role of intuitions in philosophical thought experiments like the famous Gettier cases, which overnight found acceptance by the philosophical community in their aim to refute the view that knowledge is justified true belief. While Williamson expects “armchair methods to play legitimately a more dominant role in future philosophy” (Williamson 2009, p. 126), he thinks that “we should stop talking about intuition” (Williamson 2004b, p. 152). This does not impress proponents of what we call an intuition-based account of thought experiments, and probably for good reasons, given the problems in Williamson’s approach (see, e.g., Dohrn 2016; Ichikawa and Jarvis 2009; Schaffer 2017), and the strong empirical evidence in favour of the positive role that intuitions does play in human cognition (see Myers 2004).

What we term the “intuition–based account” of thought experiments comes in a naturalistic version (see Brendel 2004; Gendler 2007), and in a Platonic version (see Brown 1991a [2011]). We begin with a discussion of the latter. Brown holds that in a few special cases we do go well beyond the old empirical data to acquire a priori knowledge of nature (see also Koyré 1968). Galileo showed that all bodies fall at the same speed with a brilliant thought experiment that started by destroying the then reigning Aristotelian account. The latter holds that heavy bodies fall faster than light ones ( H > L ). But consider Figure 6, in which a heavy cannon ball ( H ) and light musket ball ( L ) are attached together to form a compound object ( H + L ); the latter must fall faster than the cannon ball alone. Yet the compound object must also fall slower, since the light part will act as a drag on the heavy part. Now we have a contradiction: H + L > H and H > H + L . That’s the end of Aristotle’s theory. But there is a bonus, since the right account is now obvious: they all fall at the same speed ( H = L = H + L ).

Figure 6. Galileo: “I don’t even have to look”

Brown claims this is a priori (though still fallible) knowledge of nature, since there are no new data involved, nor is the conclusion derived from old data. Moreover, is it some sort of logical truth (for a technical challenge of this claim see Urbaniak 2012). This account of thought experiments can be further developed by linking the a priori epistemology to accounts of laws of nature that hold that laws are relations among objectively existing abstract entities. It is thus a form of Platonism, not unlike Platonic accounts of mathematics such as that urged by Kurt Gödel.

The two most often repeated arguments against this sort of Platonism are: it does not identify criteria to distinguish good from bad thought experiments, and it violates the principle of ontological parsimony. These seem weak objections. Perhaps they find widespread acceptance because Platonism seems to be unfashionable these days (see Grundmann 2018), given the general popularity of various forms of naturalism. If intuitions really do the job in a thought experiment, the first objection is weak because neither rationalists nor empiricists have a theory about the reliability of intuitions. So the objection should be that intuitions probably just do not matter in human cognition. However, there are good reasons to question the truth of this claim (see Myers 2004). This is not to marginalize the problems that arise when admitting intuitions as a source of knowledge and justification, especially in philosophy (see Hitchcock 2012).

As for the second objection, the appeal to Occam’s razor is in general problematic when it is employed to rule out a theory. Whatever we eliminate by employing the principle of parsimony, we can easily reintroduce it by an inference to the best explanation (see Meixner 2000). And this is exactly what a Platonist contends his or her Platonism about thought experimenting to be, while conceding that the Platonic intuition appears miraculous. But are they really more miraculous than sense perception, which seems similar in many respects to Platonic intuition? One might want to say yes, because supposedly we have no clue at all how Platonic intuition works but we do have some idea about the nature of sense perception. We know that if an object is far away it appears smaller in vision, and under certain light conditions the same object can look quite different. However, is it really impossible to state similar rules to capture the nature of Platonic intuition? If you are drunk or lack attention you most probably will not be very successful in intuiting anything of philosophical value.

A review of the relevant psychological literature will reveal further criteria that could be employed to identify good and bad conditions for Platonic intuition while thought experimenting. Yet, proponents of the naturalistic version of the intuition–based account wonder how necessary Platonism is once this move is entertained in defence of the reliability of intuitions (see Miščević 2004). Elke Brendel defines intuitions as mental propositional attitudes accompanied with a strong feeling of certainty. In her view, we can tell two stories to make sense of their cognitive power and plasticity. One story relates to our biological constitution and evolutionary past. The other is about membership in specialized communities. Brendel’s account raises many questions, but it is difficult to resist its appeal. A universal set is appealing to anyone not trained in logic because most things we are familiar with can come in sets, such as books, tables, and philosophers. A set of all sets seems intuitively plausible. The intuition disappears once you worked yourself through the problems arising from the idea of a set of all sets. Brendel is quick to insist that such relativity of our intuitions doesn’t imply that they are cognitively useless. Without intuitions, we probably wouldn’t have knowledge, and thought experiments are sometimes the only way to access the intuitions that guide us in our cognitive lives (see Brendel 2004).

John D. Norton is the most influential advocate of what we call “the argument view” of thought experiments (see Norton 1991, 1993, 1996, 2004a,b, 2008). Even though the argument view seems to be a natural option for empiricists, it seems that most empiricists find Norton’s argument view too strong. For this reason, many participants in the debate about thought experiments place themselves between the extreme views of Norton and Brown, which function as useful foils for apparently more moderate outlooks. Perhaps (with tongue in cheek) they could agree with Bernard Shaw on the virtues of moderation, when Shaw said of the typical member of the middle class that he is moderately honest, moderately intelligent, and moderately faithful to his spouse. Norton claims that any thought experiment is really a (possibly disguised) argument; it starts with premises grounded in experience and follows deductive or inductive rules of inference in arriving at its conclusion. The picturesque features of any thought experiment which give it an experimental flavour might be psychologically helpful, but are strictly redundant. Thus, says Norton, we never go beyond the empirical premises in a way to which any empiricist would object.

There are three objections that might be offered against Norton. First, his notion of argument is too vague. However, this might not be the best objection: arguments can be deductive (which are perfectly clear) or inductive. If the latter are unclear, the fault is with induction, not with Norton’s argument view. Second, it is argued that Norton simply begs the question: every real world experiment can be rephrased as an argument, but nobody would say that real world experiences are dispensable. The account does not address the question: where do the premises come from? A thought experiment might be an essential step in making the Norton-style reconstruction. Third, a thought experiment that is presented in argument form loses its typical force. The soft-point in Brown’s Platonism is linked to the strength of Norton’s account because Norton claims that any other view implies a commitment to “asking the oracle.” “Imagine an oracle that claims mysterious powers but never delivers predictions that could not be learned by simple inferences from ordinary experience. We would not believe that the oracle had any mysterious powers. I propose the same verdict for thought experiments in science” (Norton 1996, pp. 1142–1143). Defenders of empiricist alternatives deny this dispensability thesis. Brendel (2018) offers a most comprehensive review of merits and perils of the argument view.

“Conceptual constructivism”, as we could call it, is among the empiricist alternatives to the argument view. The position has been taken up by Van Dyck (2003) to account especially for Heisenberg’s ɣ-ray microscope; but also by Gendler (1998) to makes sense of Galileo’s falling body thought experiment. Gendler’s proposal was advanced in more general terms by Camilleri (2014) in order to establish a firm middle ground between the views of Norton and Brown. Conceptual constructivism was first proposed by Thomas Kuhn (1964). He employs many of the concepts (but not the terminology) of his well-known Structure of Scientific Revolutions . On his view a well-conceived thought experiment can bring on a crisis or at least create an anomaly in the reigning theory and so contribute to paradigm change. Thought experiments can teach us something new about the world, even though we have no new empirical data, by helping us to re-conceptualize the world in a new way. Accordingly, some have entertained the option of conceptual constructivism in the form of a Neo-Kantian reading of Einstein’s famous clock in the box thought experiment. Such an approach is inspired by Michael Friedman’s proposal to conceive of scientific revolutions as times when a Kantian kind of natural philosophy plays a major role in guiding scientists from one paradigm to another. The work of Kuhn left us with a puzzle: if scientific rationality is absolutely dependent on a paradigm, and if during scientific revolutions one paradigm replaces another, not in degrees but absolutely, comparable to a “Gestalt” switch, then this transition from one paradigm to the next cannot be a matter of scientific rationality. Are scientific revolutions irrational periods in the history of science? Not necessarily; some kind of natural philosophy may guide the process. Friedman has a Kantian natural philosophy in mind; his proposal did not earn wide acceptance, but the problem remains (see Fisch 2017). Be that as it may, it is true that thought experiments are a valuable currency in times of scientific revolution. For example, Lennox (1991) has argued that the revolution brought about by Charles Darwin in 1859 was made possible by thought experiments (among other things, of course).

What we might term “experimentalism” encompasses a wide range of different approaches which all advance the view that thought experiments are a “limiting case” of ordinary experiments. Experimentalism was proposed first by Ernst Mach (1897 and 1905). He defines experimenting in terms of its basic method of variation and its capacity to destroy prejudices about nature. According to Mach, experimenting is innate to higher animals, including humans. The thought experiment just happens on a higher intellectual level but is basically still an experiment. At the centre of thought experimenting is a “Gedankenerfahrung”, an experience in thought. Such an experience is possible because thought experiments draw from “unwillkürliche Abbildungen von Tatsachen” (non-arbitrary images of facts) acquired in past experiences of the world. Some thought experiments are so convincing in their results that an execution seems unnecessary; others could be conducted in a real-world experiment, which is the most natural trajectory of a scientific thought experiment. In any case thought experiments can result in a revision of belief, thereby demonstrating their significance for scientific progress. Mach also appreciates the didactic value of thought experiments: they help us to realize what can be accomplished in thinking and what cannot.

In the spirit of Mach, Sorensen (1992) has offered an aspiring version of experimentalism that accounts for thought experiments in science and philosophy, and tackles many of the central issues of the topic. Sorensen claims that thought experiments are “a subset of unexecuted experiments” (1992, p. 213). By their logical nature they are paradoxes that aim to test modal consequences of propositions. The origin of our capacity of thought experimentation is explained in terms of Darwinian evolution (as in Genz 1999, pp. 25–29), though the explanation has been criticized to be only little more than a ‘just so story’ that fails, on a posteriori grounds, to epistemically underwrite that capacity (see Maffie 1997). Others are more optimistic (see Shepard 2008).

Experimentalism does not have to take a naturalistic turn as it does in Sorensen’s case. In a number of contributions Marco Buzzoni has defended a Neo-Kantian version of experimentalism (see Buzzoni 2004, 2007, 2008, 2011, 2011b, 2013, 2013b). Buzzoni (2008) argues for the dialectical unity of thought experiments and real-world experiments. Thought experiments and real-world experiments are claimed to be identical on the “technological-operational” level, and at least in science, one is impossible without the other: without thought experiments there wouldn’t be real-world experiments because we would not know how to put questions to nature; without real-world experiments there wouldn’t be answers to these questions or experience from which they could draw. Given the many scientific thought experiments that cannot be realized in the real-world, Buzzoni might be conflating thought experiments with imagined experiments to be carried out in the real-world (see Fehige 2012, 2013b; and Buzzoni 2013b).

Idealizations are common in both real experiments and thought experiments. So-called Aristotelian idealization might ignore, say, the colour of a falling object. Galilean idealizations ignore some physical aspects, such as air friction, to get at the underlying physics (McMullin 1985). So-called Platonic idelization goes beyond this and ignores what would be actually seen even in a Galilean idealization. For instance, a rapidly moving object in special relativity would not look contracted, but rather would look rotated (surprisingly, this phenomenon is not well known). This rotation is ignored as an irrelevant optical phenomenon to yield the correct thought experiment visualization, which is the well-known Lorentz contraction (Brown 2013).

The last of the many accounts that emerged in the discussion about thought experiments is what could be called the “mental–model account.” It attracts the most followers (see Andreas 2011; Bishop 1998; Cooper 2005; Gendler 2004; Palmieri 2003; Nersessian 1992, 1993, 2007; McMullin 1985; Miščević 1992, 2007, 2021). When we conduct a thought experiment, according to champions of this view, we manipulate a mental model instead of the physical realm: “The general claim is that in certain problem-solving tasks people reason by constructing a mental model of the situations, events, and processes that in dynamic cases can be manipulated through simulation” (Nersessian 2018, p. 319). Like physical models, mental models are non-propositional in nature. This means first of all “that the carefully crafted thought–experimental narrative focuses on the construction of a model of a kind of situation and manipulating that model through simulation affords epistemic access to certain features of current representations in a way that manipulating propositional representations using logical rules cannot” (Nersessian 2018, pp. 319–320). A narrative functions as a kind of user-manual for building the model, but it isn’t identical to a thought experiment. The biggest problem for the mental–model account is to explain how something non-propositional like a mental model can make an impact on the propositional realm, which happens when a thought experiment causes a revision in beliefs.

The mental–model approach is one of the most promising of all the accounts the literature on thought experiments has to offer, and this for several reasons. First, it does not seem to be much of a stretch to draw connections to the intuition–based account. In fact, intuitions maybe the missing link to connect the essentially non-propositional activities surrounding mental models, on the one hand, and the propositional aspects of thought experiments, on the other. After all, thought experiments involve propositional reasoning, and somehow the non-propositional and propositional aspects of thought experiments must be linked in any account of thought experiments. This is urgent insofar as thought experiments are credited with a meaningful role in theory discovery and theory choice. Second, the mental–model approach also allows for inclusion of important elements of experimentalism and the argument–view. Thought experiments are realized in the mind on mental models, and the method of variation is employed such that the results of the experiment may be subject to a careful reconstruction of propositional lines of reasoning to submit it for careful assessment and critique. Third, the mental–model approach enables us to bring an aspect into focus that has been widely neglected in the discussion so far: the bodily component of (thought) experiments. The exception is the work of the late David Gooding (1992, 1993, 1994, and 1999). Fourth, in critical engagement with such naturalistic proposals, those theories of the body may be put to work that the philosophical school of phenomenology has produced (see Fehige and Wiltsche 2013). To be welcomed, therefore, is the entry of phenomenology into the discussion on thought experiments (see Hopp 2014; Wiltsche 2018). Fifth, the mental–model account also relates naturally to the most intriguing discussions about the role of literary fiction in thought experiments.

Some have placed “literary fiction on the level of thought experiments” (Swirski 2007, p. 6). There are two readings of such a claim. According to the first, some literary fiction may be of cognitive power due to the fact that they are thought experiments. In other words, we shouldn’t outright reject the idea that literature can be of cognitive value. Dystopian novels such as Orwell’s 1984 and Huxley’s Brave New World are obvious examples. According to the second reading, the power of thought experiments is partially a function of the narrative that conveys it. The work of Novalis remains relevant for the exploration of this link between narrative development and thought experiment: experimental writing and experiments on imagined scenarios go hand in hand; words and thoughts coincide; mind and matter are entangled (see Daiber 2001). According to the mental–model approach, both readings have a valid point. Literary fiction and narratives of thought experiments can be powerful in establishing mental models in such a way that we can even learn new things about the world at times from the fictional elements of them. The common denominator is the work on mental models each may facilitate. It is in this context that an appreciation can grow for Catherine Elgin’s theory of exemplification to argue against the “valorization of truth in epistemology” (2004, p. 113). This is also the place to consider Andras Kertesz’s (2015) work on conceptual metaphor research in its relevance to the epistemological puzzle that thought experiments pose.

Finally, sixth, mention could be made of visual reasoning in mathematics, which often seems closely related to thought experiments. The standard view of mathematics is that the one and only source of evidence is a proof, and a proof is a derivation from axioms or first principles. Let’s overlook the problem of where the first principles come from. A simple example such as the following casts doubt on the standard view:

Theorem: 1 + 2 + 3 + … + n = n 2 /2 + n/2 Proof: See Figure 7.

Figure 7. Picture proof.

The proof works like this: Start at the top and work down, letting the little squares represent numbers, 1 + 2 + 3 + 4 + 5 . The total number of squares in the picture is equal to this sum. Notice also that the numbers of squares is equal to a large square with sides of length 5 that is cut in half along the diagonal, i.e., 5 2 /2 , plus the shaded bits that were cut off by the diagonal cut, i.e., 5/2 . It is plausible to claim that the diagram is a perfectly good proof of the theorem. One can “see” complete generality in the picture. Even though it only illustrates the theorem for n = 5 , somehow we can see that it works for every number, all infinitely many of them. The diagram does not implicitly suggest a “rigorous” verbal or symbolic proof. The regular proof of this theorem is by mathematical induction, but the diagram does not correspond to an inductive proof at all, since the key element in an inductive proof is the passage from n to n + 1 . The simple moral we could draw from the example is just this: We can in special cases correctly infer theorems from pictures, that is, from visualizable situations. There is an intuition and from this intuition we can grasp the truth of the theorem (see Brown 1999 [2008]).

Our assessment of the prospects of the mental–model account is very rough and speculative, though certainly not implausible. Of course, there are challenges to such a vision of a greater synthesis of the many different takes on thought experiments under the umbrella of the mental-model account. For example, some see additional support arising for the argument–view from computer simulations (see Beisbart 2012). Others find that “computational modeling is largely replacing thought experimenting, and the latter will play only a limited role in future practice of science, especially in the sciences of complex nonlinear, dynamical phenomena” (see Chandrasekharan et al. 2012, p. 239). But, there are also proposals such as that by Marcus Schulzke (2014) to think of video games philosophically as executable thought experiments. Whatever the merits of this particular proposal, future explorations of the relationship between computer simulations and thought experiments can build on outcomes of closer inquiries into it (see Behmel 2001, pp. 98–108; Di Paolo et al . 2000; El Skaf and Imbert 2013; Lenhard 2011; Stäudner 1998; Lenhard 2018). The work on the nature of the importance of scientific understanding (see, e.g., Stuart 2018) will inform that exploration as much as the fruits of continuing efforts to clarify the role of the imagination in thought experiments (see, e.g., Meynell 2014; Stuart 2017 and 2021).

We conclude with an interesting, but still relatively unexplored issue that concerns the relative importance of thought experiments in different disciplines. Physics and philosophy use them extensively. Chemistry, by contrast, seems to attract less attention in this respect. Why is this the case? Perhaps it is merely an historical accident that chemists never developed a culture of doing thought experiments. Perhaps it is tied to some deep feature of the discipline itself (see Snooks 2006). Economics and history use thought experiments, but apparently not anthropology. A good explanation would likely tell us a lot about the structure of these disciplines.

Related to this is the question of the difference, if any, between thought experiments in the sciences and those in philosophy. We have assumed throughout this entry that they are the same kind of thing. Not everyone sees them this way, so perhaps it should be considered an open question. On the one hand, philosophy and science seem to many to be different kinds of activities. That might suggest that thought experiments would differ in the two areas. On the other hand, there is a huge difference between thought experiments within a single field, e.g., Newton’s bucket attempts to establish absolute space while Schrödinger’s cat aims to show QM as then understood to be absurd. Is the difference between them less than the difference between either of them and Searle’s Chinese Room or Thomson’s violinist? The case one way or the other is not obvious. Of course, there are differences between constructive and destructive thought experiments, but this is true within any discipline. Perhaps for now the default attitude ought to be that there is no categorical difference between scientific and philosophical thought experiments. This should not be treated as a dogmatic principle, but rather a stimulus to look deeper for important subtle contrasts.

The number of papers, anthologies, and monographs has been growing immensely since the beginning of the 1990s. It might be useful to highlight that in existing literature, Kühne (2006) remains the most substantial historical study on the philosophical exploration of thought experiments. And Sorensen (1992) remains the most comprehensive philosophical study of thought experiments. More than other monographs both of these studies well exceed the author’s own systematic contribution to what is widely considered the primary epistemological challenge presented by thought experiments. Also, this bibliography does not include the many (we count about eight) popular books on thought experiments (like Wittgenstein’s Beetle and Other Classical Thought Experiments by Martin Cohen); nor do we list fiction that is related to the subject (like The End of Mr. Y by Scarlett Thomas, or God’s Debris by Scott Adams). Further, for undergraduate teaching purposes one might want to consider Doing Philosophy: An Introduction Through Thought Experiments (edited by Theodore Schick, Jr. and Lewis Vaughn, fifth edition, 2012, Boston: McGraw Hill Higher Education), and chapter 5 of Timothy Williamson’s short introduction to philosophical method (Oxford University Press, 2020). Moreover, a number of philosophical journals have dedicated part or all of an issue to the topic of thought experiments, including the Croatian Journal of Philosophy (19/VII, 2007), Deutsche Zeitschrift für Philosophie (1/59, 2011), Informal Logic (3/17, 1995), Philosophica (1/72, 2003), Perspectives on Science (2/22, 2014), Berichte zur Wissenschaftsgeschichte (1/38, 2015)), as well as TOPOI (4/38, 2019), HOPOS (1/11, 2021), and Epistemologia (12/2022). Furthermore, a companion to thought experiments exists now: The Routledge Companion to Thought Experiments was published in 2017. Each includes substantial state of the art reports. The bibliography that follows aims to list only publications that address thought experiments as such. Not included are the many specialized papers that discuss a particular thought experiment in its systematic contribution to the discussion of a particular issue (such as Putnam’s twin earth scenario to support semantic externalism). An exception is made, of course, when such work is cited. Unlike in previous versions of this entry, we no longer aim for comprehensiveness in the bibliography that follows.

• Aligica, Paul D., and Anthony J. Evans, 2009, “Thought Experiments, Counterfactuals and Comparative Analysis”, The Review of Austrian Economics , 22: 225–239.
• Andreas, Holger, 2011, “Zur Wissenschaftslogik von Gedankenexperimenten”, Deutsche Zeitschrift für Philosophie , 59: 75–91.
• Arthur, Richard, 1999, “On Thought Experiments as A Priori Science”, International Studies in the Philosophy of Science , 13: 215–229.
• Bailey, Cyril, 1950, Lucretius on the Nature of Things (translation of De Rerum Naturae ), ninth reprint, Oxford: Clarendon Press.
• Batens, Diderik, 2008, “On Possibilities and Thought Experiments”, in R. Almeder (ed.), Rescher Studies , Heusenstamm: Ontos Verlag, 29–57.
• Bealer, George, 1998, “Intuition and the Autonomy of Philosophy”, in M. DePaul and W. Ramsey (eds.), Rethinking Intuition: The Psychology of Intuition & Its Role in Philosophical Inquiry , Lanham: Rowman & Littlefield, 201–239.
• –––, 2002, “Modal Epistemology and the Rationalist Renaissance”, in T. S. Gendler and J. Hawthorne (eds.), Conceivability and Possibility , Oxford: Clarendon Press, 71–125.
• Beck, Simon, 1992, “Should we Tolerate People who Split?”, Southern Journal of Philosophy , 30: 1–17.
• –––, 2006, “These Bizarre Fictions: Thought Experiments, Our Psychology and Our Selves”, Philosophical Papers , 35: 29–54.
• Becker, Alexander, 2018, “Thought Experiments in Plato”, in M. T. Stuart et al. (eds.), The Routledge Companion to Thought Experiments , London and New York: Routledge, 44–56.
• Behmel, Albrecht, 2001, Was sind Gedankenexperimente? Kontrafaktische Annahmen in der Philosophie des Geistes – der Turingtest und das Chinesische Zimmer , Stuttgart: Ibidem.
• Beisbart, Claus, 2012, “How can Computer Simulations Produce New Knowledge?”, European Journal for Philosophy of Science , 2: 395–434.
• Belkin, Aron, and Tetlock, Philip E. (eds.), 1996, World Politics: Logical, Methodological, and Psychological Perspectives , Princeton: Princeton University Press.
• Bishop, Michael, 1998, “An Epistemological Role for Thought Experiments”, in N. Shanks (ed.), Idealization IX: Idealization in Contemporary Physics , Amsterdam/Atlanta, GA: Rodopoi, 19–33.
• –––, 1999, “Why Thought Experiments are Not Arguments”, Philosophy of Science , 66: 534–541.
• Bokulich, Alisa, 2001, “Rethinking Thought Experiments”, Perspectives on Science , 9: 285–307.
• Boniolo, Giovanni, 1997, “On a Unified Theory of Models and Thought Experiments in Natural sciences”, International Studies in Philosophy of Science , 11: 121–142.
• Borsboom, Denny, et al., 2002, “Functional Thought Experiments”, Synthese , 130: 379–387.
• Borstner, Bojan, and Gartner Smiljana (eds.), 2017, Thought Experiments between Nature and Society , Newcastle upon Tyne, UK: Cambridge Scholars Publishing.
• Brendel, Elke, 1999, “Gedankenexperimente als Motor der Wissenschaftsdynamik”, in J. Mittelstraß (ed.), Die Zukunft des Wissens. XVIII. Deutscher Kongress für Philosophie , Konstanz: UVK, 785–792.
• –––, 2004, “Intuition Pumps and the Proper Use of Thought Experiments”, Dialectica , 58: 88–108.
• –––, 2018, “The Argument View: Are Thought Experiments Mere Picturesque Arguments?”, in M. T. Stuart et al. (eds.), The Routledge Companion to Thought Experiments , London and New York: Routledge, 281–293.
• Brooks, David H. M., 1994, “The Method of Thought Experiment”, Metaphilosophy , 25: 71–83.
• Brown, James Robert, 1986, “Thought Experiments since the Scientific Revolution”, International Studies in the Philosophy of Science , 1: 1–15.
• –––, 1991 [2011], Laboratory of the Mind: Thought Experiments in the Natural Sciences , London: Routledge, Second Edition.
• –––, 1999 [2008], Philosophy of Mathematics: A Contemporary Introduction to the World of Proofs and Pictures , London and New York: Routledge, second edition.
• –––, 2004, “Why Thought Experiments Do Transcend Empiricism”, in C. Hitchcock (ed.), Contemporary Debates in the Philosophy of Science , Malden, MA: Blackwell, 23–43.
• –––, 2004b, “Peeking into Plato’s Heaven”, Philosophy of Science , 71: 1126–1138.
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• Thought Experiments , entry in the Oxford Bibliographies , by James R. Brown and Michael T. Stuart.
• Thought Experiments and Religion , entry in the Oxford Encyclopedia of Religion , by Yiftach Fehige.
• Goodies , a collection of intriguing questions in the philosophy of science, some about thought experiments, by John Norton.
• An Interactive Version of Thomson’s violin thought experiment .
• Six famous thought Experiments Explained Quickly , a video tutorial.
• Ethical Thought Experiments Like the Trolley Dilemma , a video tutorial.

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Home > Books > Urban Transition - Perspectives on Urban Systems and Environments

Future Urban Environments in Science Fiction: Initiated Thought Experiments

Submitted: 19 March 2021 Reviewed: 04 May 2021 Published: 24 May 2021

DOI: 10.5772/intechopen.98245

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Is it possible that science fiction-films have influenced modern architecture and buildings in the real world? Ideas about the design and purpose of future cities often start with visions. Science fiction can be understood as a kind of thought experiment. The experimenter, the writer or filmmaker, begins with a hypothesis and sets up initial conditions. SF writers take notice of their colleagues’ work and results; they often borrow fundamental concepts from previous generations of writers. Authors elaborate on and transform these concepts, apply and test them in new situations, and add new ideas. I argue that our capacity to imagine things and phenomena that do not yet exist is important in the process of constructing and reorganizing human life and, hence, also urban environments. The concepts of “city” and “countryside”, both of which are often projected and experienced as opposites, with contradictions and conflicts built into them, are examined. Urban Transition through some of the most influential dystopian sf-movies with Metropolis is my starting point, films where the idea of the city can be said to be the main protagonist.

• science fiction
• countryside

Author Information

Britt johanne farstad *.

• Department of Humanities, Faculty of Education and Business Studies, University of Gävle, Sweden

*Address all correspondence to: [email protected]

1. Introduction

You know, there’s one thing about Blade Runner : Yes, it’s gritty and it’s scary, and it is obvious unbelievable unequal as a future society – but the nightlife looks amazing [ 1 ].

I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhauser Gate. All those moments will be lost in time, like tears in rain. Time to die. Roy Batty, Blade Runner

Is it possible that science fiction-films have influenced modern architecture and buildings in the real world? “Urban transition” is a highly interesting topic, and I started to wonder if it was possible to find robust links between the SF-genre and modern architecture. It was almost too easy to establish connections between the sphere of fantasy and real-world architecture. A simple google-search settled the question: science fiction plus modern architecture led me directly to interviews with the architects who built the most spectacular buildings during the last decades. Furthermore, I found several articles exploring these connections. Professor of Urban Historical Geography J. R. Gold, states quite simply that the “relationship between cinematic film and the city is close and multifaceted” [ 2 ]. My own knowledge in the genre helped to ask relevant questions to the material I found. SF can be said to be an expression of a “Zeitgeist”, or ‘spirit of the age’ [ 3 ]. It became obvious in this material that certain ideas in fact have wandered from fiction to reality. Other thoughts have wandered the other way, from reality to fiction. It’s an ongoing dance of ideas.

What are the prominent features of the science fiction genre (SF) that make it relevant to focus on in relation to ideas and discussions about “urban transition”? Although technology plays an important role in many SF texts and films, the genre is intensely occupied with ideas about human life, its meaning and purpose, and other existential questions. SF is often labeled “a literature of ideas”, which indicates that the genre provides good models of thought concerning science and ethics and provokes and challenges ideas about the human condition. SF literature is by tradition didactic, and many writers and creators working within the genre have played important roles in the ethical and social debates of their time [ 4 ].

As technology and science are both integral parts of contemporary culture and society, the effects of science on human lives and societies have increased. Given that SF is characterized by hypothetical thought experiments, it is well suited to debates about how future cities could or should be organized. Scientist and SF author Karlheinz Steinmüller argues that SF is the mythology of the modern, scientific age [ 5 ] and states that SF “has become a unique medium for discussing science and technology, their prospects and hazards, and more generally their social and cultural impacts” [ 6 ]. As part of postmodern culture, the SF genre has influenced the different forms of media. Steinmüller writes that for “many scientists and engineers, science fiction provides the imaginary of their visions” and claims that SF can be understood as a kind of thought experiment similar to those in science: “The experimenter – the writer – begins with a hypothesis and sets up initial conditions” [ 7 ]. Steinmüller argues that in some ways, “SF is quasi-scientific and, like science itself, a collective enterprise. Like scientists, SF writers take notice of their colleague’s work and results; they borrow the fundamental concepts from previous generations of writers. They elaborate on and transform these concepts, apply and test them in new situations, and add new ideas” [ 7 ]. Hence, I find it relevant to explore ideas about the city in SF films and investigate whether or how SF visions have influenced the design and structure of the actual cities that are built? Here, I look at the ideas and the fantasies that appear in architectural visions and real life.

Three connecting topics concerning urban transition are discussed in this chapter. In the first part I argue that our capacity to imagine things and phenomena that do not yet exist is important in the process of constructing and reorganizing human life and, hence, also urban environments. SF as “initiated thought experiments” is discussed in this part with Metropolis (1927) as the starting point.

In the next part I examine the concepts of “city” and “countryside”, both of which are often projected and experienced as opposites, with contradictions and conflicts built into them. The ancient notion, in fact built on mythological tales, of one as better and the other as worse is constantly reproduced in fiction and film. According to these myths , human life takes place between the mythical and lost Garden of Eden and the New Jerusalem to come. One significant occurrence between these events is when human beings build their first great city, the Tower of Babel . Hence, mythological conflicts influence the creation of SF films, many of which are often occupied with existential questions. This is important when it comes to ideas about the organization of city life, as well as in depictions of life in the countryside. I argue that notions about what is preferable can be found in some of the mythological tales that have been reproduced in fiction.

In the last part I discuss the connections between SF films and the construction of modern cities around the world. My idea is that our fantasies affect what we want to achieve in the real world. Furthermore, I ask if some of these fantasies and ideas stem from literature and film. For over a century, SF films have depicted futuristic cities. Some of these cities are bright, shiny and positive, while others are described as dark, dirty and rough. In these chapter focus is on the dystopian branch of SF: film history become relevant when it turns out that prominent architects in our time are deeply influenced by the visual visions they experienced as young persons. However, we may need to look elsewhere to find film visions of green, sustainable, future cities, as these do not seem to appear in SF films. Where, I wonder, might such film visions be found?

2. “In the beginning there was Metropolis”

In some of the most significant SF films and their visions of the future, the City can be said to be the protagonist [ 8 ]. In a review of SF films and authentic modern architecture, film critic Rich Haridy states: “In the beginning there was Metropolis ” [ 8 ]. Metropolis , by Fritz Lang (1927), is a vision of a vertical city and an important film when it comes to real world images of the city. The film is also depicting a society with deep conflicts between classes in the society with a harsh hierarchy between rulers and the ruled. A much later film that was strongly influenced by Metropolis is Blade Runner , by Ridley Scott (1982). Here, hypothetical visions of architectural concepts of the future city are visualized in a more technically advanced and globalized world than in Lang’s film, which was created in the early days of the industrial world. Blade Runner is set in 2019 and is an example of how earlier ideas are developed and reproduced. With the film, Scott builds a bridge between 1927 and 1982 in film history. Social hierarchies are even grimmer than in Metropolis : the rich have left the planet for another world. Acid rain is falling to let us understand that Earth’s climate is seriously disrupted.

In Blade Runner 2049, also by Ridley Scott (2017), the themes and motifs are developed further. This is a sequel to Blade Runner released in 1982 and according to the film’s narrative, 30 years have passed. In both films, Scott deals with the climate crisis and the challenges that future generations may have to deal with in megacities. In these visions of future cities and city life, architecture, infrastructure and human life are representations of extreme abundance and extreme impoverishment, highly advanced technology and collapsing systems, decaying buildings and shattered infrastructure. The vision of future life in cities that is portrayed in this SF film is bleak. The rich and healthy have left Earth to live in new settlements in the colonies. Even in the film Cloud Atlas by Wachowski, Wachowski and Tykwer (2012), human beings have fled from the cities to try to make a living for themselves elsewhere [ 9 ]. Fantastic technology and architecture are hidden and forgotten. The only way for human beings to survive is for them to leave the planet and find a new and greener one.

Frederik Pohl writes in “The Politics of Prophecy”, that to “speak of ‘political science fiction’ is almost to commit a tautology, for I would argue that there is very little science fiction, perhaps even that there is no good science fiction at all, that is not to some degree political” [ 10 ]. Pohl was the initiator of the New York association “The Futurians”, which was active in the late 1930s and early 1940s. This was a group of SF writers, critics, publishers and illustrators who believed that “SF fans should be forward-looking (‘futurian’) and constructive” [ 11 ]. Socially critical SF was important because:

Their injection of social consciousness into the fandom world had an enduring effect at a time when the pulp stories were beginning to address the future of authoritarian social orders. Graduating to the ranks of professional editors and writers at the end of the decade, they eventually formed something of a counterculture operating against the established power of the field's publishers and editors [ 11 ].

Media researcher Jenkins writes that “the Futurians were committed to the idea that science fiction might function as a vehicle for social criticism and political transformation” [ 12 ]. Philosopher Hans Jonas argues that fiction provides thought models for ethics and morality and writes that the “serious side of science fiction lies precisely in its performing such well-informed thought experiments, whose vivid imaginary results may assume the heuristic function here proposed. (See, e.g., A. Huxley’s Brave New World)” [ 13 ].

Jonas highlights Aldous Huxley’s Brave New World as an example of an initiated thought experiment and argues that in hypothetical thought experiments there is an opportunity to find ethical foundations through statements that can claim probability. This is sufficient where they should not be evidence but illustrations [ 14 ]. As society is becoming increasingly complex, and technological development is rapidly accelerating, it is becoming increasingly difficult for people to have an overview. Jonas writes that “the knowledge of the possible” is “heuristically sufficient for the doctrine of principles” [ 14 ]. A complex narrative can accordingly help to get a grip of the challenges that lie ahead [ 15 ]. The SF genre, as the Zeitgeist of modernity and an artistic expression with the ability to put real, complex, moral and ethical problems under the microscope, can visualize possible futures. By analyzing futuristic fiction by scientifically trained authors as “initiated thought experiments”, as Hans Jonas puts it, it is possible to say something about the hopes and fears that well-informed researchers associate with new technologies. Further, the SF genre’s fictional representations of science and technology make it possible to discuss complex thought models based on hypothetical consequences. In Hans Jonas’ opinion, these initiated thought experiments can add knowledge about ethical difficulties related to scientific research. Prof. J. R. Gold’s opinion is that it “is seldom the case that the film-maker reveals the future city with extraordinary accuracy, and it unquestionably pays to be sanguine about science-fiction film as a medium of prediction” [ 16 ]. At the same time, he thinks that “such film can supply us with an accessible and intriguing route into a series of core issues about representations of place” [ 16 ]. As Hans Jonas even Gold thinks that the more distinguished SF-films “can supply incisive images that help us to pose questions about the relationship of people and place, and where that relationship is headed.”

SF films can thus be helpful when it comes to discussions about different kinds of dangers. One problem that becomes obvious in my project is that futuristic cities are mostly portrayed in ruins in SF films, and it is too late to survive in them. People instead flee to the countryside or to other worlds in order to survive. Prof. J. R. Gold writes that

Representation of the city stems from the development and constant reiteration of a handful of urban prototypes. Certainly, in the 75 years since Metropolis codified the essence of the vertical city, only the future noir city has emerged as a fully-fledged alternative [ 17 ].

Ursula Heisse also states that dystopian “views of the cities make up the overwhelming majority of futuristic urban literature and film” [ 18 ]. In short, in dystopias the big cities are always in ruins and life is over. The future exists on alien green planets or in rural districts outside the city gates. I will come back to this futuristic vision – which in fact may well be a SF vision of the “New Jerusalem”.

3. Human life between the garden of Eden and the New Jerusalem

The archetypical concepts of “city”, “country” and “countryside” are relevant in relation to “urban transition” and SF films depicting images of future cities. Modern SF has repeatedly reproduced contrasts between the city and the wilderness surrounding it. The city can be enclosed in huge plastic domes - thus making it easy to differentiate between city life and rural life. Another commonly used narrative is that of old cities that have fallen into disrepair, where memories of lost greatness are uncovered in reminiscences of decay. Narratives of a future city environment in which humans move in the shadow of hostile artifacts are also common. The central idea is the city as fundamentally dystopian. In this text I mention three of the most influential twentieth century dystopias, Zamiatin’s We (1924), Huxley’s Brave New World (1932) and Orwell’s Nineteen Eighty-Four (1949). These books and the film-adaptions films have laid a fundament for the following dystopias. The narrative take place in cities from which escape is impossible. The city is an artificial place, is potentially dangerous and will eventually disrupt. In the end it will be a danger to human beings.

Scientists warn for an ecological disaster at a global level. At present, with global warming and rising sea levels as a result, it is obvious that many of our megacities around the world are facing challenges. Cities located near the coast will be dramatically affected by rising sea levels. Consequently, an important topic in scientific research, politics and popular culture is the narrative about the threat of great floods. This archaic theme has been communicated over thousands of years by word of mouth, as written and printed texts and now through modern films. In SF, several parallel movements occur simultaneously and human life in cities is scrutinized more than ever. As SF expert John-Henri Holmberg states: “The city is the focal point of our civilization, and images of the city of the future bring into sharp relief the expectations and fears with which we imagine the future of civilization” [ 19 ].

In my view, mythical contradictions and conflicts have been built into concepts and ideas about the city and the countryside. These contradictions have often been reproduced, and mythical conflicts have influenced the creation of fiction and to a certain degree people’s mindset when thinking about future megacities. The starting point for this idea is to be found in the first chapters of Genesis , the first book in the Old Testament , and in the last chapters in Revelation , the last book in the New Testament . Hence, we look backwards before looking forwards.

To understand the ideas behind this conflict we will turn to the first mythological home of mankind - the Garden of Eden - as it is described in Genesis :

Genesis 2:8 And the Lord God planted a garden eastward in Eden; and there he put the man whom he had formed. 2:9 And out of the ground made the Lord God to grow every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil. 2:10 And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads. 2:15 And the Lord God took the man, and put him into the garden of Eden to dress it and to keep it [ 20 ].

As we know, Adam and Eve failed to live according to God’s will and were therefore banished from the flourishing garden. As yet there is no city in sight. The next narrative is the first fratricidal murder in our narrative history. Cain murders his brother Abel and is expelled from the land. He is said to build a city, which is the first to mentioned in these ancient stories:

Genesis 4:15 And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him. 4:16 And Cain went out from the presence of the Lord, and dwelt in the land of Nod, on the east of Eden. 4:17 And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch [ 21 ].

After these mythological events a famous city is built. The Tower of Babel rose in the land, perhaps built on the foundation Cain once made:

Genesis 11:4 And they said, Go to, let us build us a city and a tower, whose top may reach unto heaven; and let us make us a name, lest we be scattered abroad upon the face of the whole earth. 11:5 And the Lord came down to see the city and the tower, which the children of men builded. 11:7 Go to, let us go down, and there confound their language, that they may not understand one another's speech. 11:8 So the Lord scattered them abroad from thence upon the face of all the earth: and they left off to build the city [ 22 ].

This is one of the most important myths to be retold and reproduced from the biblical tales: how God denigrated the hard work of human beings. The annihilation is extreme – their language is confused so that they can no longer communicate. Hence, they can no longer make elaborate plans and agree on great achievements. Too advanced technological skills and advanced constructions are equated with megalomania and struck down. It is like eating the apple once again. The Great Flood and the Tower of Babel are two major events in which God strikes hard against people’s creative powers.

The Biblical Apocalypse is described in the Book of Revelation in the New Testament. First, the dystopian future to come is described. Finally, the heavenly city is revealed to the prophet as it emerges from the sky:

Revelation 21:10 And he carried me away in the spirit to a great and high mountain, and shewed me that great city, the holy Jerusalem, descending out of heaven from God, 21:19 And the foundations of the wall of the city were garnished with all manner of precious stones [ 23 ].

Revelation 22:14 Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city. 22:15 For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie [ 24 ].

The future paradise is a city with the tree of life in the middle of it. It is in fact the vision of Eden restored, this time within the walls of a marvelous city made of gold and all the emeralds they could ever name. Even the future city of peace and love needs high walls to keep evil out. This heavenly city is obviously a place for the chosen ones, the privileged and the blessed.

The Garden of Eden is an idea about the lost utopia. A major part of mankind’s mythical and historical existence thereafter plays out between two contrasting ideas: The heavenly Garden of the long-gone Paradise Eden and the Paradise to come. The last of this complex book that we call the Bible ends up in a narrative circle, where the first main tropes are combined into one. The New Jerusalem is about doom and salvation and, finally, the City represents salvation from disaster and chaos. There are laws, order and structure, high walls, streets, clean house bodies – everything built with the most precious of materials. Chaos still exists but it is outside the gates. The shining city represents enchantment, order and security, as opposed to chaos in the unbridled landscape outside the city walls. The narrative about the return to Paradise happens in harmony with nature. The city in Genesis, the Tower of Babel, represents a society that collapses into chaos.

On the other hand, the much-acclaimed SF author Ursula K. Le Guin’s novels emanate from another idea. One of her novels is called The Word for World is Forest (1972) and is a landmark when it comes to contrasting the position of the city and rural areas. Her narrative uses nature as the starting point, the focal point, and cities are the unfamiliar and unnatural habitat. She depicts Nature as the normal place for human beings to live and thrive in contrast to glittering – and hence artificial – cities. The novel can be said to start a movement and growing sub-genre in SF literature called “eco-fiction”. In his dissertation Places of Rest: in worlds of Ruin: Havens in Post-Apocalyptic Fiction (2021), Andreas Nyström investigates the lost paradise as a focal point in the dystopian branch of the sf-genre. He writes that the “pastoral sensibilities expressed in many post-apocalyptic havens are part of a millennia-long, cross-cultural history of mythologization of paradisiacal gardens” [ 25 ].

The “New Jerusalem” in Revelations represents a glittering utopian city, where important elements from the lost Paradise are incorporated, such as significant trees and the river that according to the first myth is said to float through the paradise city to come. Our mythological history and background are important allusions and intertexts in the narratives that follow, as mythological ideas and contradictions are recreated and reproduced in modern narratives.

4. “The Burj Khalifa is not just a skyscraper, and Metropolis is much more than a film”

Robust evidence of connections between fiction and modern architecture exists in several articles about one of the most famous architects of our time, Adrian Smith (1944) [ 1 , 26 ]. Among other assignments, Smith is a Senior Fellow of The Design Futures Council. This is an interdisciplinary network of design, product and construction leaders exploring global trends, challenges and opportunities to advance innovation and shape the future of industry and the environment [ 27 ]. What is interesting in this context is that references to a film immediately pop up in interviews with the architect. The vision of the biblical New Jerusalem is here as well. In The Wizard of Oz we find an emerald city with deep roots in this very old narrative:

21:19 And the foundations of the wall of the city were garnished with all manner of precious stones. The first foundation was jasper; the second, sapphire; the third, a chalcedony; the fourth, an emerald… [ 23 ]

The film version of The Wizard of Oz (1939) is referred to as a vision and his pictorial starting point. As Adrian Smith designed Burj Dubai, he claims to have been thinking of “another metropolis: the forest of gleaming towers that is the Emerald City, as glimpsed by Dorothy and her friends from the poppy field in the film version of The Wizard of Oz ”. Smith says that the vision from the film was in his mind when he planned the extravagant skyscraper in Dubai, “although in a subliminal way. I didn’t research the way it looked -- I just remembered the glassy, crystalline structure coming up in the middle of what seemed like nowhere” [ 28 ]. The reference to The Wizard of Oz is also important in an older presentation of Adrian Smith’s work:

If Chicago were the modern-day Land of Oz, the Trump Tower would be its Emerald Palace. (…) As I approach the beaming building there’s an extra bounce in my step, and I can’t help but think of Dorothy, Toto and her storybook friends skipping along the yellow brick road. Instead of a yellow road, the tower has the Chicago River – and the two have a lot in common. Like the river, the tower is made up of curves and is predominantly blue [ 29 ].

In the interviews with Smith, the connection between the film and the architect’s visions is highlighted. The ideas for the design of some of the most startling buildings in modern times originate from films depicting fantasies. Can we then say that ideas forego reality?

What is striking now, is the tendency for some futuristic cities, such as Dubai, to be so explicitly influenced by SF visions that are profoundly rooted in dystopian perspectives. Inspired by video games and big Hollywood cinema, this new wave of big oil-led design is dominated by multi-billionaires developing futuristic worlds. Dubai is a hotbed of Gulf futurism. Syd Mead, Hollywood’s much-acclaimed futuristic conceptualist, designer, artist and one of the key designers behind Blade Runner, says that the Middle East is a “fantastic example of how reality is catching up with the future as the size, scope and vision of some of the region’s projects clearly show. I would like to be a part of the region’s horizon and help shape it for a better tomorrow” [ 30 ]. Mead claims that life imitates art, and art imitates life, and that this ceaseless movement back and forth can be seen explicitly in the evolution of our cities over the last century [ 30 ].

In an article investigating SF cities, Rich Haridy wonders “How our future visions influence the cities we build” [ 26 ]. Haridy refers to Fritz Lang, the “granddaddy of all futuristic urban visions” and Metropolis as a vision of a future city that has influenced a century of filmmakers. Haridy also claims that Metropolis has influenced a century of architects:

Taking us through the looking glass, one of the strangest ironies in 21st century architecture is the growing influence films such as Blade Runner are having on real-life constructions. The recently termed movement, gulf futurism, describes a very particular brand of architecture and urban design that is powering through the Middle East [ 26 ].

Once again, architect Adrian Smith’s spectacular buildings are used as an example of how fiction impacts modern architecture. Even Haridy stresses that Adrian Smith’s hugely influential practice in Chicago, which designs most of the world’s supertall skyscrapers, has shown that “his inspiration for designing the Burj Khalifa came from watching Wizard of Oz as a child — the Emerald City being these gleaming towers looming high above flat, endless plains” [ 1 ].

John R. Gold has examined SF films and the role of futuristic depictions of cities. In the article Under Darkened Skies: The City in Science-fiction Film, Gold writes: “Nevertheless, if Metropolis is regarded as the work that crystalized the screen portrayal of the vertical city, then Ridley Scott’s Blade Runner (1982) codified the future noir city. Blade Runner created a bridge in film development” [ 31 ]. Metropolis is a “dystopian vision of a vertical city and Blade Runner develops and transforms the idea to the modern world of 1982” [ 8 ]. It is possible that the idea behind this vertical city design in films is that future megacities will be dominated by massive skyscrapers and the “urban footprint will not spread outward but instead we will build taller and taller buildings that will ultimately encompass all aspects of a human society within a single tiered building” [ 8 ].

However, it is more likely that the vertical city was an effective way of visualizing inequalities in economic and political power: the high city rises from a fundament consisting of a base of workers and slaves living and producing necessary goods underground. For much of the 20th century, the vertical city idea became intrinsically interlinked with dystopian SF visions. The rich lived at the top and the poor scrambled about on the grim streets below in exactly the same way that Fritz Lang pictured the future city in 1927. This literal illustration of a class-based hierarchy has been portrayed in a number of interesting SF novels and films from the early days of film to more recent stories, such as Elysium (2013) and Altered Carbon (2018) [ 8 ]. The world of Blade Runner is a compact industrial, ethnic and lingual mishmash. The city center, where the enormous Tyrell concern is situated, is constructed upwards. Images of the city with skylines and flying vehicles remind us of Metropolis , but the Tyrell building reminds us even more of an ancient Mayan temple and paintings of the Tower of Babel. The Fredersen headquarters in Metropolis is called the New Tower of Babel. As we can see, Biblical allusions are frequent in these narratives.

Stephen Graham, Professor of Cities and Society with a particular focus on cities and speculative fiction, sees a somewhat unsettling trend playing out in some of these new, large-scale architectural visions. In Vertical: The City from Satellites to Bunkers (2016), he describes the almost shocking experience of landing in Dubai in 2020 and seeing the 830-metre high Burj Khalifa: “It felt as though we’d arrived on some vast stage set for a highly sanitised sequel to Blade Runner made by Disney” [ 32 ]. He describes the horizontal vs. vertical constructions and their impact on the landscape, water supplies and so on. The first priority in the new megacities is hardly sustainability. In the article “How science fiction dystopias became blueprints for city planners” [ 1 ]. Graham says that there is “a really startling and disturbing similarity between a lot of these sci-fi vertical dystopias and the current practice in, say, the Gulf, where the elites inhabit their penthouses and fly around in helicopters and business jets while literally thousands of workers are dying every year to construct these edifices” [ 1 ]. He emphasizes that: “These are not just imagined cityscapes: The way these putative futures are imagined have enormous implications for our contemporary urban life” [ 1 ]. These examples thus make it possible to suggest that the ideas behind planning and construction stem from ideals and archetypes shaped out of images and impressions inflicted on us as individuals and as collective consumers of pictures, films, fiction and narratives. Super-rich builders are obviously attracted by the idea of the vertical city.

The time may have come when the two separated worlds will be combined. The best parts of life in the green, flourishing rural world merged with the best parts of urban life to make life more sustainable for more people. Green sustainable cities emerge as visions in the fictive and political landscapes. In SF, the Lost Paradise and The Tower of Babel have been portrayed time and time again. It may be time for the New Jerusalem to be the new vision to be investigated in narrative form.

5. Green cities: a synthesis and a sustainable vision?

In the introduction to the film The Human Scale – Bringing Cities to life (2012), film director Andreas Møl Dalsgaard states that: “The megacities are a reality, and it looks a lot like the visions of the science fiction-films, gigacities are soon to be” [ 33 ]. More than half of the world’s population live in cities and, among other things, face the challenges of climate change, urban development and overpopulation. Urbanization is rapidly increasing. It is estimated that by 2050, 70 per cent of the global population will be living in urban areas [ 34 ]. Climate change adaptation, green cities and smart cities are buzzwords. Stimulating urban transition and transformation to achieve sustainable and resilient cities is one of the greatest challenges of our time [ 35 ]. Policy documents and political agendas are debated and written at national and global levels: “In this unprecedented era of increasing urbanization, and in the context of the 2030 Agenda for Sustainable Development, the Paris Agreement, and other global development agreements and frameworks, we have reached a critical point in understanding that cities can be the source of solutions to, rather than the cause of, the challenges that our world is facing today” [ 36 ]. The idea is that “well-planned” and “well-managed” urbanization can be a powerful tool for sustainable development for both developing and developed countries [ 36 ].

Urban transition implies that urban environments will undergo important changes that are critical from many points of view. Agreeing on sustainable solutions to the multitudes of challenges that humanity is facing is difficult due to conflicting values and views about natural resources [ 37 ]. One obstacle that can be difficult to overcome is determining what a sustainable city really is. Hence, we need to discuss the city as a phenomenon: one that is both an abstract idea and a physical and mental reality. Ideas about “a city” consist of resilient stereotypes and mental conceptions, where the countryside or rural environments are the most recognizable opposites and juxtapositions.

Cities are economic and administrative centers in nations and societies, as opposed to the peripheral areas outside a city’s boundaries: the rural countryside that provides the city with necessary goods. Cities thus represent power, and rural areas less power. City dominance is manifested in complex buildings, advanced logistical systems and infrastructure to make all parts of the city function. Status and power are manifested in the number of luxurious homes and business districts for the people in power. At the same time, there are poor districts within cities, bad housing and crowded spaces for the less fortunate living there. In good times, cities represent abundance, law and order, often in contrast to insufficiency and less control outside the city’s domain. The precondition for people to live in cities is that the countryside provides them with the necessary goods and resources. In times of economic problems, war, famine or pandemics, the situation is drastically reversed. Major cities are the most vulnerable and will be attacked first if war threatens. People will try to escape to the countryside, which will then become a place of shelter and survival.

Cities can be said to be in a constant state of transition . The sustainable and dignified conditions that we try to realize in modern cities, and the notions of how modern urban societies could be organized, start with ideas. These ideas affect how we think that cities could be constructed, what ought to be prioritized, what we consider to be a good life and how a good life can be organized. What role might SF have in envisioning the future? Hopes and fears are often concretized in the SF genre’s hypothetical narrative method: what will be the result if …? There are plenty of dystopias and doomsday stories and a noticeable lack of optimistic narratives.

6. Conclusions

Earlier I stated that we may need to look elsewhere to find film visions of green, sustainable, future cities, as these do not seem to appear in SF films. The great blockbuster films continue to reproduce the archetypical narrative of the conflicts between cities and rural districts. The disasters are due to environmental problems as we know them from scientific and news reports all over the world. Tipping points are pandemics, overpopulation, rising sea-levels, a new ice age, genetic manipulation, AI, intelligent robots and so on, all of which are said to cause the world as we know it to collapse. The stage may be set in intergalactic contexts, but the story remains the same: the countryside, which may be our old Earth, in conflict with new cities, in the form of interstellar societies to which the rich and powerful have emigrated. SF films, as opposed to novels in this case [ 38 ], seem stuck in archetypes as well as being dependent on big money.

Despite this, films are created by actors other than large corporations and money machines. Many of them also tell other and different stories. Under the parole “More Than Movies: A Movement”, the San Francisco Green Film Festival is working to tell other stories. As a non-profit organization “committed to using the power of film to bring audiences into the global conversation on environmental solutions” [ 39 ]. And to “spark green ideas and actions”. According to the presentation, it is “dedicated to sharing stories from the environmental front-lines that inspire, inform, and ignite change” [ 40 ]. Under the heading “Films for the Earth”, educational films are collected on a website in the same spirit to inform that change is necessary and possible to achieve [ 41 ]. Perspectives are turned upside down: finally, human beings are at the center of the planned transformations in cities. In a film called Edible City: Grow the Revolution , activists and initiatives from people living in cities demonstrate how they grow their own food. People spread knowledge, develop local economic cycles and find hopeful solutions to monumental problems. The film demonstrates how people develop models for healthy and sustainable local food systems that are environmentally friendly and crisis resistant [ 42 ]. In the film called The Nature of Cities , architecture professor Timothy Beatley visits several cities to investigate how city planners, landscape architects, ecologists and residents view the symbiosis between cities and rural landscapes. Here, two archetypes merge into visions about the new cities.

Filmmakers are creating new and sustainable visions of futuristic cities in which the inhabitants produce food and take nature into their towns. Plants grow on house walls and on roofs, while vegetables grow in open green areas in the middle of the city. The filmmaker’s idea is to inspire people around the globe to make this happen and be part of a solution for sustainable city life. They film to visualize new futures but without the cataclysmic conflicts that SF films are in need of for the dramaturgy to work. In SF-films we find dystopias which can be helpful when we can discuss what went wrong, but we seldom find the utopias where inspiring ideas of solutions are found. When it comes to literature it’s a totally different story [ 43 ]. The circle of ideas continues the dance, where reality and fiction affect one another. Despite this, blockbuster SF films about well organized, beautiful and thriving green cities are still missing in the world.

• 1. https://www.inverse.com/article/18488-science-fiction-future-city-planning-dubai-skyscrapers-dystopia
• 2. J. R. Gold, “Under darkened skies: the city in science fiction film”, Geography, 86(4), 337.
• 3. Zeitgeist means the general intellectual, moral, and cultural climate of an era. Zeit means time and Geist means spirit, i.e. spirit of the age.
• 4. Britt Farstad, The Glass Bead Player : New Worlds, Ethics and Androcentrism in Peter Nilson’s Science Fiction Novels , Umeå University Press 2013, p. 33 ff.
• 5. Karlheinz Steinmüller, “Science Fiction and Science in the Twentieth Century”, p. 352 in Companion to Science in the Twentieth Century , ed. John Krige and Dominique Pestre, (London - Routledge 2003).
• 6. Karlheinz Steinmüller, “Science Fiction and Science in the Twentieth Century”, p. 339 in Companion to Science in the Twentieth Century , ed. John Krige and Dominique Pestre, (London - Routledge 2003).
• 7. Karlheinz Steinmüller, “Science Fiction and Science in the Twentieth Century”, p. 360 in Companion to Science in the Twentieth Century , ed. John Krige and Dominique Pestre, (London - Routledge 2003).
• 8. https://newatlas.com/science-fiction-cities-future-urban-visions-architecture/55569/
• 9. Another example is Elysium by Neill Blomkamp (2013).
• 10. Donald M. Hassler and Clyde Wilcox, ed., Political Science fiction , p. 7. (University of South Carolina Press, 1996).
• 11. http://web.mit.edu/m-i-t/science_fiction/profiles/pohl.html
• 12. Henry Jenkins, Science fiction, media and imagination, p. 1. http://web.mit.edu/m-i-t/science_fiction/profiles/pohl.html
• 13. Hans Jonas, The imperative of Responsibility: In Search of an Ethics for the Technological Age , p. 30.
• 14. Hans Jonas, The imperative of Responsibility: In Search of an Ethics for the Technological Age , p. 29.
• 15. Martha Nussbaum, Narrative Emotions : Becketts Genealogy of Love , p. 225ff., p. 228ff. I Ethics: Symposium on Morality and Literature , Vol. 98, January 1988, nr. 2, ed. Russel Hardin (The University of Chicago Press 1988).
• 16. J. R. Gold, “Under darkened skies: the city in science fiction film”, Geography, 86(4), 347.
• 17. J. R. Gold, “Under darkened skies: the city in science fiction film”, Geography, 86(4), 345.
• 18. https://www.thenatureofcities.com/2019/05/27/imagining-future-cities-in-an-age-of-ecological-change/
• 19. http://www.sf-encyclopedia.com/entry/cities
• 20. https://classic.biblegateway.com/passage/?search=genesis+2&version=KJV
• 21. https://classic.biblegateway.com/passage/?search=Genesis+4&version=KJV
• 22. https://classic.biblegateway.com/passage/?search=Genesis+11&version=KJV
• 23. https://classic.biblegateway.com/passage/?search=revelation+21&version=KJV
• 24. https://classic.biblegateway.com/passage/?search=Revelation+22&version=KJV
• 25. Andreas Nyström, Places of Rest: in worlds of Ruin , p. 141.
• 26. Rich Haridy, 2018, https://newatlas.com/science-fiction-cities-future-urban-visions-architecture/55569/
• 27. https://en.wikipedia.org/wiki/Design_Futures_Council https://web.archive.org/web/20071112040544/http://www.di.net/
• 28. http://smithgill.com/news/chicago_sun-times_27_nov/
• 29. https://blueprintchicago.wordpress.com/2010/05/27/the-trump-tower/
• 30. https://www.albawaba.com/news/syd-mead-visit-dubai
• 31. Under darkened skies: The City in Science- fiction Film , John R. Gold, Geography Volume 86(4), p. 340.
• 32. https://www.amazon.co.uk/dp/B01LXRV1T8/ref=rdr_kindle_ext_tmb , (2016) preface pp. 1-3.
• 33. https://www.doclounge.se/films/the-human-scale-bringing-cities-to-life The Human Scale – Bringing Cities to Life , Director, Andreas Møl Dalsgaar, Denmark 2012.
• 34. international_guidelines_on_urban_and_territorial_planning_-_handbook_, p. 3.
• 35. https://www.sciencedirect.com/science/article/pii/S1364032118304398
• 36. https://uploads.habitat3.org/hb3/NUA-English.pdf
• 37. https://www.sciencedirect.com/science/article/pii/S1364032118304398#bib3
• 38. Good examples on literature on this topic are Kim Stanley Robinson’s novels Red Mars (1992), Green Mars (1993), Blue Mars (1996) and New York 2140 (2017).
• 39. https://www.greenfilmfest.org/about
• 40. https://www.greenfilmfest.org/filmarchive
• 41. https://filmsfortheearth.org/en/issues/urbanization-smart-cities
• 42. Directed by Andrew Hasse and Carl Grether, UK 2014.
• 43. A few resourse that can be mentioned are https://cambridgeecofiction.org/resources/ and a book by William H. Baarschers, Eco-facts and Eco-fiction: Understanding the Environmental Debate , (Routledge 1996)

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Introduction to "Science Fiction and Philosophy"

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Targaryen Thought Experiments: Do Science Fiction and Fantasy Examples Aid or Obfuscate Student Learning?

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Adam Irish, Nicole Sherman, Levi Watts, Targaryen Thought Experiments: Do Science Fiction and Fantasy Examples Aid or Obfuscate Student Learning?, International Studies Perspectives , Volume 24, Issue 1, February 2023, Pages 1–19, https://doi.org/10.1093/isp/ekab016

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Several recently published international relations and criminal justice writings, textbooks, and supplements focus on using science fiction and fantasy texts to teach social science theories. This article investigates how science fiction and fantasy examples affect student learning compared to documentary films. We use mixed methods to conduct two studies on the use of science fiction and fantasy in political science and criminal justice classrooms. In the first study, we divide up a large lecture class, comparing how examples from the HBO series Game of Thrones versus documentary films affect student learning about the United Nations and peacekeeping. Our second study uses a combination of interviews and surveys to assess how students apply various criminological theories to the 1997 film Gattaca versus a documentary. Our research reveals that science fiction and fantasy examples neither help nor harm student learning. However, incorporating examples from fictional worlds may alienate some students, affecting their enjoyment of class and perception of preparedness. Most importantly, we find that the use of fictional examples creates an interpretive barrier in the classroom. Thus, we recommend judicious use of science fiction and fantasy examples. When fictional examples are used, we encourage student preparation and extensive debriefing.

Resumen: Varios escritos, libros de texto y suplementos sobre relaciones internacionales y justicia penal publicados recientemente se centran en el uso de textos de ciencia ficción y fantasía para enseñar teorías de Ciencias Sociales. En este artículo se investiga cómo los ejemplos de ciencia ficción y fantasía inciden en el aprendizaje de los estudiantes en comparación con los documentales. Utilizamos una combinación de métodos para realizar dos estudios sobre el uso de la ciencia ficción y la fantasía en las clases de Ciencias Políticas y Justicia Penal. En el primer estudio, tomamos una clase magistral y la dividimos para comparar cómo los ejemplos de la serie de HBO "Juego de Tronos" y las películas documentales inciden en el aprendizaje de los estudiantes sobre la ONU y el mantenimiento de la paz. En el segundo estudio, utilizamos una combinación de entrevistas y encuestas para evaluar el modo en que los estudiantes aplican diversas teorías criminológicas a la película Gattaca de 1997 en comparación con un documental. Con nuestra investigación se revela que los ejemplos de ciencia ficción y fantasía no enriquecen ni perjudican el aprendizaje de los estudiantes. Sin embargo, la incorporación de estos ejemplos puede hacer que algunos estudiantes se pierdan en el mundo de la ciencia ficción, y afectar su capacidad de disfrutar de la clase y su percepción de los conocimientos adquiridos. Lo más importante que observamos es que el uso de ejemplos ficticios crea una barrera interpretativa en el aula. Por lo tanto, recomendamos el uso criterioso de ejemplos de ciencia ficción y fantasía. Cuando se utilizan ejemplos ficticios, es fundamental preparar a los estudiantes y ofrecerles una vasta cantidad de información.

Résumé: Plusieurs écrits, manuels et suppléments récemment publiés sur les relations internationales et la justice pénale se concentrent sur l'utilisation de textes tirés de la science-fiction et du fantastique pour enseigner les théories des sciences sociales. Cet article enquête sur la manière dont les exemples issus de la science-fiction et du fantastique affectent l'apprentissage des étudiants par rapport aux films documentaires. Nous avons employé des méthodes mixtes pour mener deux études sur l'utilisation de la science-fiction et du fantastique dans les cours de sciences politiques et de justice pénale. Dans la première étude, nous avons divisé une grande classe de cours magistraux en comparant la façon dont les exemples tirés de la série Game of Thrones de HBO affectaient l'apprentissage de l'ONU et du maintien de la paix par les étudiants par rapport aux films documentaires. Notre deuxième étude s'est appuyée sur une combinaison d'entretiens et d'enquêtes pour évaluer la manière dont les étudiants appliquaient diverses théories pénales au film Bienvenue à Gattaca de 1997 par rapport à un documentaire. Notre recherche révèle que les exemples issus de la science-fiction et du fantastique ne favorisent ni ne nuisent à l'apprentissage des étudiants. Cependant, l'intégration d'exemples tirés de mondes fictifs peut aliéner certains étudiants, affectant ainsi leur plaisir en classe et leur perception de la préparation. Plus important encore, nous constatons que l'utilisation d'exemples issus de la fiction crée une barrière à l'interprétation dans la classe. Nous recommandons par conséquent une utilisation judicieuse des exemples tirés de la science-fiction et du fantastique. Lorsque des exemples tirés de la fiction sont utilisés, nous préconisons une préparation et un débriefing approfondi des étudiants.

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Apocalypse philosophy: What science fiction teaches us about existence

• The best science fiction presents philosophical thought experiments that make us ask deep questions.
• Here, we look at a broad range of apocalyptic and post-apocalyptic scenarios and isolate four themes common to them.
• As it turns out, science fiction has a lot to teach us about existence.

The best kind of science fiction is philosophy. Yes, lasers and teleporters are cool, but science fiction asks big questions. It imagines alternate worlds and exaggerated scenarios. It presents you with “What would life be like” thought experiments.  The Matrix  is about knowledge and truth, and  Star Trek  asks how we should form a perfect society.  Gattaca  considers reproductive ethics, and  Starship Troopers  is about just war theory.  Isaac Asimov ‘s rules for robots are more important than ever. Science fiction, when it’s done well, stays in your head for a long time.

One of the most popular subgenres of science fiction features apocalyptic and post-apocalyptic worlds.  The Walking Dead  ran for 11 seasons, and  The Hunger Games  has four movies.  World War Z  sold 15 million copies worldwide, and  Station Eleven  has won numerous awards. Here, we examine the deeper, philosophical question behind common apocalyptic ideas.

Who do we save?

When Worlds Collide  is about a cosmic catastrophe, and the people of Earth plan for their imminent extinction. A rogue star has been spotted, and it’s set to destroy our planet. Similar storylines are also found in  Deep Impact ,  2012 , and  The Mist . In each case, humanity is left with only enough resources to save a small portion of the entire race. Who, then, do we save?

According to Immanuel Kant, all rational agents have the same right to life and free choice as anyone else. No one is to be treated as a means to an end but as valuable in themselves. For Kant, then, a lottery system (as in  Deep Impact ) would likely be the best. For utilitarians, we should save the ones who will provide future humanity with the best outcomes: the doctors, engineers, and the most accomplished. In reality, the world is almost certainly Nietzschean. The Übermensch of our time — the generals and government officials — will be first on the spaceships. It’s not even a secret that if there were a nuclear war, it’s the politicians who would get first place in the vaults and bunkers.

How shall we rebuild society?

Post-apocalyptic fiction almost always features a portion of society rebuilding and reconstructing a world from the dusty and deserted remnants.  The Walking Dead  and  Fallout  feature pockets of very different gangs or tribes that reestablish drastically different communities. But one of the bestselling examples of this is  The Stand , where post-apocalyptic America is divided into the goodies in Nebraska and the baddies in Las Vegas. These scenarios raise a powerful question: How would we build society if we could start from scratch?  It’s something that would make a good podcast.

This echoes a well-known thought experiment from John Rawls known as the “original position.” Essentially, it asks us to imagine that you were transported to a new society, but you didn’t know at all what class, age, or sex you would be or how much wealth you would have. How would you engineer the structures and prejudices of that society to maximize your chances of being happy and fulfilled? What post-apocalyptic world would be fairest to everyone?

To what extent should we try to control nature?

One of the defining characteristics of  Homo sapiens’  success is our ability to control, tame, or push back against nature. We cut and  burned down forests , we dammed rivers to stop floods, and we domesticated livestock. And yet, a lot of science fiction is based on scenarios where humans have gone too far, resulting in genetically engineered monstrosities or climate catastrophe. All of which raises the question: To what extent should we try to control nature?

It is naïve to assume we shouldn’t control nature at all. Antibiotics, air conditioning, and structural engineering all involve us manipulating the natural order of things. They involve killing and destroying. Francis Bacon and René Descartes saw controlling nature as essential to civilization. It was about the rational controlling the irrational; it was order from chaos. When the first humans cut down a clearing in the forest to build homes, this was no doubt true. But there comes a tipping point: a point when damaging nature also damages humanity. Apocalyptic fiction is a great tool to examine when and where that point comes.

What matters when you’re the last person alive?

28 Days Later  opens with a lonely, confused man wandering the empty streets of London. Here is a man left alone in one of the busiest cities in the world.  Oryx and Crake ,  I Am Legend , and  Wall-E  all feature characters fending for themselves in a barren, eerily silent world. They all raise an existentially important question: Does anything matter more than our relationships?

At first glance, a post-apocalyptic world seems pretty fun. No bosses, no queues, and no financial worries. You can drive the fastest cars, live in the biggest mansions, and binge on all the Dom Pérignon you want. But after that, what? What do you do?

One of the most powerful stories to explore this idea is Cormac McCarthy’s  The Road . This features a father and son wandering a desolate, cold landscape. They’re not alone; there are bandits and horrors, but all that matters is the two of them and the love they have for each other. When the world is on fire, and there’s both everything and nothing to do, what matters most? It’s the people you love.

When real-life adventurer Christopher McCandless died alone in an abandoned bus in Alaska, his journal contained the line, “Happiness is only real when shared.” Without other people, what is the point of anything?

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SCIENCE FICTION THOUGHT EXPERIMENTS IN BIOETHICS

• Science fiction, bioethics, thought experiment,James R. Brown, John D. Norton, mental-modeling, mental modelling, mental models, Nancy J. Nersessian, Nenad Miščević, Tamar Gendler, schemas, literature, Geordie McComb, literary thought experiments, narrative, ethics. scientific thought experiment, philosophy, speculative fiction, Nancy Kress

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• DOI: 10.1002/9781118922590.CH0
• Corpus ID: 261730269

Introduction: Thought Experiments: Science Fiction as a Window into Philosophical Puzzles

• Susan Schneider
• Published 29 February 2016

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Taoist philosophy in chinese science fiction: a comparison between zhuangzi and broken stars, 4 references, intelligence unbound: the future of uploaded and machine minds, adaptive flight control with living neuronal networks on microelectrode arrays, the man on the moon, immortality, and other millennial myths: the prospects and perils of human genetic engineering., minds, brains, and programs, related papers.

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AgriLife Today

Texas A&M AgriLife's digital magazine and newsroom

Research says high energy fire influences prescribed burn effectiveness

Fuel, timing proven to increase fire's success against woody plant encroachment.

June 13, 2024 - by Adam Russell

Fighting woody plant encroachment with prescribed burns may be more effective than land managers previously thought.

A study by Bill Rogers, Ph.D., professor in the  Texas A&M College of Agriculture and Life Sciences Department of Ecology and Conservation Biology , showed prescribed burns could be an effective tool for land managers to use against woody plants. The key is to use available vegetative fuel, like stockpiled grasses, and weather conditions to the burn’s advantage.

The recent study, “ Exotic Herbivores and Fire Energy Drive Standing Herbaceous Biomass but do not Alter Compositional Patterns in the Semiarid Savanna Ecosystem ,” was published in Applied Vegetation Science .

Timing, fuel load impact on prescribed burns

Rogers and his team studied the effectiveness of different “fire energies” for controlling resprouting woody plant species like juniper and mesquite and herbivores’ impact on potential fuel loads for prescribed burns. Fire energy refers to a fire’s burning intensity, including radiant energy released by flames.

The research was conducted at Texas A&M AgriLife Research Station in Sonora , located in a semi-arid savanna in southwest Texas.

Rogers said the amount of available fuel and timing of the burn greatly impacted the outcome when using fire to manage woody plants. His study showed that land managers should consider access by grazing animals, including cattle and non-native species like axis deer, as well as conditions like temperature, relative humidity and fuel moisture content when utilizing prescribed burns.

“There has been some doubt about fire’s ability as an effective tool once an ecosystem becomes encroached by woody shrubs and trees,” Rogers said. “But what we found is that hotter, drier conditions and the amount of available fuel heavily influences how effective a prescribed burn can be at reducing the density of these invasive woody plants.”

A new prescription for prescribed fire

Rogers said prescribed fire has been historically viewed as a poor option for land managers to clear junipers and mesquite once they are established in a location. Mechanical removal or chemical application seemed to be the most effective tools available despite the considerable cost associated with their implementation.

But Rogers said the traditional timing and conditions under which prescribed fires have been utilized has limited the ability to kill brushy plants. Traditionally, state and federal agencies have recommended setting fires under the “80-20-20 rule.” The rule suggests fires should not be set above 80 degrees, below 20% relative humidity and with winds exceeding 20 mph.

The 20-mph wind restriction makes good sense, because fires can escape containment under windy conditions, Rogers said. But the limitations on temperature and relative humidity have led most burns to occur at the least effective time, according to his study.

For more than a decade, students in Rogers’ lab began using “high energy” fire during summer drought when temperatures were over 100 degrees and plants had low moisture content. They found these high-intensity fires could kill non-sprouting juniper and achieved a significantly higher kill rate in mesquite, which can sprout back when left alive.

This led the U.S. Department of Agriculture National Resource Conservation Service to adjust some restrictions, and county commissioners in charge of burn bans began allowing land managers to set fires in more effective conditions.

“We started to see that setting fires in mild conditions is largely what led to their ineffectiveness,” Rogers said. “We set fires in these hotter, drier conditions with lower fuel moisture and started to see woody plant mortality and significant reductions in woody plant density.”

Experiments provide science for prescribed burns

Rogers said timing and weather conditions are very important, but fuel loads are also an important component to produce enough fire energy to kill woody plants. This will likely require land managers to restrict access by grazing animals to allow vegetation to grow and provide adequate vegetative fuel for the burn to reach higher energy levels.

His team set up 72 randomized 30 foot by 30 foot experimental plots at the Sonora station to identify various ranges of fuel and fire energy. Researchers restricted livestock, including goats, sheep and cattle, from grazing access ranging from zero, limited and full access.

Rogers noted factors that affected fuel loads within the experimental plots. For example, researchers were unable to completely restrict axis deer, which are invasive grazers, from the plots. He also noted how grass productivity factored into fuel buildup, whether from lack of soil moisture or in areas with rocky and/or marginal soils.

Researchers added fuel like hay and dried juniper in measured amounts to randomized plots before burns to simulate higher fuel loads than could be achieved before the experiment. The team used video and infrared video cameras stationed 40 feet in the air via a boom lift to capture each burn. Other instrumentation above and below ground was used to collect temperatures created by the fire.

“The infrared camera and instrumentation allowed us to track heat signatures and the fire’s energy throughout each burn, and that gave us a better understanding of the relationship between fuel loads, weather conditions and fire energy,” Rogers said. “We want to eventually be able to give a land manager our best recommendations to make prescribed fire most effective as a tool to control woody plants.”

Prescribed burns as a tool

There were other claims about prescribed fire that Rogers’ study also dispelled. While high-energy fires will kill woody plants, it does not negatively impact soils or native plants in these vegetative communities, including seed grasses.

The study showed high-energy fires did not “sterilize the soil” or seal the soil like clay in a kiln, he said. High-energy fires also did not disrupt soil microbiome communities or native plant recovery. 

High-energy fires did not decrease the base plant community dynamics, he said. For instance, “bud banks” of grasses bounced back even better after the burn, and succulents like Bacchus recovered with no long-term negative impacts.

Rogers said he is focused on providing science-based solutions for landowners and land managers. He believes the study answered several foundational questions related to the efficacy and impact of prescribed burns.

“Science is showing that prescribed burns can be an important and beneficial tool for controlling invasive woody plants, improving ag production potential for farmers and ranchers and habitat for wildlife while also reducing fuel loads that could lead to catastrophic wildfires,” he said. “We hope this study can be part of that conversation.”

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What Are Thought Experiments?

• First Online: 30 September 2021

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Suppose you have a friend who is very naïve when it comes to physics. He follows his commonsense view, uninformed by high-school physics, that heavier bodies fall faster than the light ones: the heavier the body is, the faster it falls. That’s it.

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