hypothesis definition us government

• More from M-W
• To save this word, you'll need to log in. Log In

Definition of hypothesis

Did you know.

The Difference Between Hypothesis and Theory

A hypothesis is an assumption, an idea that is proposed for the sake of argument so that it can be tested to see if it might be true.

In the scientific method, the hypothesis is constructed before any applicable research has been done, apart from a basic background review. You ask a question, read up on what has been studied before, and then form a hypothesis.

A hypothesis is usually tentative; it's an assumption or suggestion made strictly for the objective of being tested.

A theory , in contrast, is a principle that has been formed as an attempt to explain things that have already been substantiated by data. It is used in the names of a number of principles accepted in the scientific community, such as the Big Bang Theory . Because of the rigors of experimentation and control, it is understood to be more likely to be true than a hypothesis is.

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch, with theory being the more common choice.

Since this casual use does away with the distinctions upheld by the scientific community, hypothesis and theory are prone to being wrongly interpreted even when they are encountered in scientific contexts—or at least, contexts that allude to scientific study without making the critical distinction that scientists employ when weighing hypotheses and theories.

The most common occurrence is when theory is interpreted—and sometimes even gleefully seized upon—to mean something having less truth value than other scientific principles. (The word law applies to principles so firmly established that they are almost never questioned, such as the law of gravity.)

This mistake is one of projection: since we use theory in general to mean something lightly speculated, then it's implied that scientists must be talking about the same level of uncertainty when they use theory to refer to their well-tested and reasoned principles.

The distinction has come to the forefront particularly on occasions when the content of science curricula in schools has been challenged—notably, when a school board in Georgia put stickers on textbooks stating that evolution was "a theory, not a fact, regarding the origin of living things." As Kenneth R. Miller, a cell biologist at Brown University, has said , a theory "doesn’t mean a hunch or a guess. A theory is a system of explanations that ties together a whole bunch of facts. It not only explains those facts, but predicts what you ought to find from other observations and experiments.”

While theories are never completely infallible, they form the basis of scientific reasoning because, as Miller said "to the best of our ability, we’ve tested them, and they’ve held up."

• proposition
• supposition

hypothesis , theory , law mean a formula derived by inference from scientific data that explains a principle operating in nature.

hypothesis implies insufficient evidence to provide more than a tentative explanation.

theory implies a greater range of evidence and greater likelihood of truth.

law implies a statement of order and relation in nature that has been found to be invariable under the same conditions.

Examples of hypothesis in a Sentence

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'hypothesis.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Greek, from hypotithenai to put under, suppose, from hypo- + tithenai to put — more at do

1641, in the meaning defined at sense 1a

Phrases Containing hypothesis

• counter - hypothesis
• nebular hypothesis
• null hypothesis
• planetesimal hypothesis
• Whorfian hypothesis

Articles Related to hypothesis

This is the Difference Between a...

This is the Difference Between a Hypothesis and a Theory

In scientific reasoning, they're two completely different things

Dictionary Entries Near hypothesis

hypothermia

hypothesize

Cite this Entry

“Hypothesis.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/hypothesis. Accessed 21 Aug. 2024.

Kids Definition

Kids definition of hypothesis, medical definition, medical definition of hypothesis, more from merriam-webster on hypothesis.

Nglish: Translation of hypothesis for Spanish Speakers

Britannica English: Translation of hypothesis for Arabic Speakers

Britannica.com: Encyclopedia article about hypothesis

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Can you solve 4 words at once?

Word of the day.

See Definitions and Examples »

Get Word of the Day daily email!

Popular in Grammar & Usage

Plural and possessive names: a guide, 31 useful rhetorical devices, more commonly misspelled words, absent letters that are heard anyway, how to use accents and diacritical marks, popular in wordplay, 8 words for lesser-known musical instruments, it's a scorcher words for the summer heat, 7 shakespearean insults to make life more interesting, 10 words from taylor swift songs (merriam's version), 9 superb owl words, games & quizzes.

• Search Search Please fill out this field.

What Are Twin Deficits?

• First Twin: Fiscal Deficit
• Second Twin: Current Account Deficit
• Current Account Deficit

Twin Deficit Hypothesis

The bottom line.

• Government Spending & Debt
• Government Debt

The Twin Deficits of the U.S.

Economies that have both a fiscal deficit and a current account deficit are often referred to as having "twin deficits." This means that government revenues are lower than the government's expenses and that the price of the country's imports is greater than the income from its exports.

The United States has had twin deficits since the early 2000s. The opposite scenario—a fiscal surplus and a current account surplus—is generally viewed as preferable, but much depends on the circumstances. China is often cited as an example of a nation that has enjoyed long-term fiscal and current account surpluses.

Key Takeaways

• The U.S.'s twin deficits usually refer to its fiscal and current account deficits.
• A fiscal deficit is a budget shortfall. A current account deficit, roughly speaking, means a country is sending more money overseas for goods and services than it is receiving.
• Many economists argue that the twin deficits are correlated, but there is no clear consensus on the issue.

The First Twin: Fiscal Deficit

A fiscal deficit , or budget deficit, occurs when a nation's spending exceeds its revenues. The U.S. has run fiscal deficits almost every year for decades.

Intuitively, a fiscal deficit doesn't sound like a good thing. But Keynesian economists argue that deficits aren't necessarily harmful, and  deficit spending can be a useful tool for jump-starting a stalled economy. When a nation is experiencing a recession , deficit spending on infrastructure and other big projects can contribute to aggregate demand. Workers hired for the projects spend their money, fueling the economy and boosting corporate profits.

Governments often fund fiscal deficits by issuing bonds . Investors buy the bonds, in effect loaning money to the government and earning interest on the loan. When the government repays its debts, investors' principal is returned. Making a loan to a stable government is often viewed as a safe investment. Governments can generally be counted on to repay their debts because their ability to levy taxes gives them a reliable way to generate revenue.

The combined current accounts deficit and budget deficit as a percentage of U.S. GDP, as of July 2023.

The Second Twin: Current Account Deficit

A current account is a measure of a country’s trade and financial transactions with the rest of the world. This includes the difference between the value of its exports of goods and services and its imports, as well as net payments on foreign investments and other transfers from abroad.

In short, a country with a current account deficit is spending more overseas than it is taking in. Again, intuition suggests this isn't good. Those countries must continually borrow money to make up the shortfall, and interest must be paid to service that debt. For smaller, developing countries, especially, this can leave them exposed to international investors and markets.

A sustained deficit of exports versus imports may indicate a country has lost its competitiveness, or reflect an unsustainably low savings rate among the deficit-running country's people.

Current Account Deficit: It's Complicated

But like budget deficits, the truth about current accounts isn't that simple. In practice, a current account deficit can reflect that a country is an attractive destination for investment , as is the case with the U.S. Consider that advanced economies such as the U.S. often run current account deficits while developing economies typically run surpluses.

Some economists believe a large budget deficit is correlated to a large current account deficit. This macroeconomic theory is known as the twin deficit hypothesis. The logic behind the theory is that government tax cuts, which reduce revenue and increase the deficit, result in increased consumption as taxpayers spend their new-found money. The increased spending reduces the national savings rate , causing the nation to increase the amount it borrows from abroad.

When a nation runs out of money to fund its fiscal spending, it often turns to foreign investors as a source of borrowing. At the same time, the nation is borrowing from abroad, its citizens are often using borrowed money to purchase imported goods. At times, economic data supports the twin deficit hypothesis. Other times, the data does not.

Which Country Has the Highest Budget Deficit?

According to World Bank data, Croatia has the highest level of public debt, with a total deficit of 688% of the country's GDP as of 2021. Note that for many countries, the most recent data was unavailable or out of date.

Which Country Has the Highest Trade Deficit?

According to World Bank data, Mozambique has the highest trade deficit as of 2022. The country's current account balance shows a deficit of 35% of the country's GDP. Note that many countries did not have recent figures to report.

Why Is a Trade Deficit Bad?

A trade deficit means that a country is importing more goods than it exports, resulting in high demand for foreign currency and low demand for domestic currency. A consistent trade deficit can be harmful to the domestic economy because local producers do not have enough demand for their goods.

Twin deficits refer to a combined shortfall between a country's government revenues and its export income. Some economists believe that these deficits are related, because low tax revenues can result in increased borrowing from abroad. The United States consistently runs both budget deficits and trade deficits, which some economists predict may lead to unexpected disruptions.

Reuters. " US Twin Deficits Matter for the Dollar, Just Not that Much ."

Cornell Law School. " Taxing Power ."

World Bank. " Central Government Debt, Total (% of GDP) ."

World Bank. " Current Account Balance (% of GDP). "

• Terms of Service
• Editorial Policy
• Privacy Policy

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center

• Where was science invented?
• When did science begin?

scientific hypothesis

Our editors will review what you’ve submitted and determine whether to revise the article.

• National Center for Biotechnology Information - PubMed Central - On the scope of scientific hypotheses
• LiveScience - What is a scientific hypothesis?
• The Royal Society - Open Science - On the scope of scientific hypotheses

scientific hypothesis , an idea that proposes a tentative explanation about a phenomenon or a narrow set of phenomena observed in the natural world. The two primary features of a scientific hypothesis are falsifiability and testability, which are reflected in an “If…then” statement summarizing the idea and in the ability to be supported or refuted through observation and experimentation. The notion of the scientific hypothesis as both falsifiable and testable was advanced in the mid-20th century by Austrian-born British philosopher Karl Popper .

The formulation and testing of a hypothesis is part of the scientific method , the approach scientists use when attempting to understand and test ideas about natural phenomena. The generation of a hypothesis frequently is described as a creative process and is based on existing scientific knowledge, intuition , or experience. Therefore, although scientific hypotheses commonly are described as educated guesses, they actually are more informed than a guess. In addition, scientists generally strive to develop simple hypotheses, since these are easier to test relative to hypotheses that involve many different variables and potential outcomes. Such complex hypotheses may be developed as scientific models ( see scientific modeling ).

Depending on the results of scientific evaluation, a hypothesis typically is either rejected as false or accepted as true. However, because a hypothesis inherently is falsifiable, even hypotheses supported by scientific evidence and accepted as true are susceptible to rejection later, when new evidence has become available. In some instances, rather than rejecting a hypothesis because it has been falsified by new evidence, scientists simply adapt the existing idea to accommodate the new information. In this sense a hypothesis is never incorrect but only incomplete.

The investigation of scientific hypotheses is an important component in the development of scientific theory . Hence, hypotheses differ fundamentally from theories; whereas the former is a specific tentative explanation and serves as the main tool by which scientists gather data, the latter is a broad general explanation that incorporates data from many different scientific investigations undertaken to explore hypotheses.

Countless hypotheses have been developed and tested throughout the history of science . Several examples include the idea that living organisms develop from nonliving matter, which formed the basis of spontaneous generation , a hypothesis that ultimately was disproved (first in 1668, with the experiments of Italian physician Francesco Redi , and later in 1859, with the experiments of French chemist and microbiologist Louis Pasteur ); the concept proposed in the late 19th century that microorganisms cause certain diseases (now known as germ theory ); and the notion that oceanic crust forms along submarine mountain zones and spreads laterally away from them ( seafloor spreading hypothesis ).

• Encyclopedia ›

Definition Hypothesis

A hypothesis is a statement or conclusion based on, for example, statistical observations . A hypothesis must refer to at least two variables ; otherwise a connection cannot be established. The statement made in a hypothesis goes beyond the current state of actual knowledge, i.e., a hypothesis is a (new) established presumption. Hypotheses are to be phrased in a clear and precise manner, to ensure that their statement can be empirically confirmed or refuted.

An example of a hypothesis based on statistical analysis is the statement "people having a  healthy lifestyle live longer."

Please note that the definitions in our statistics encyclopedia are simplified explanations of terms. Our goal is to make the definitions accessible for a broad audience; thus it is possible that some definitions do not adhere entirely to scientific standards.

• Hyperparameter
• Hallucination

• Privacy Policy

Home » What is a Hypothesis – Types, Examples and Writing Guide

What is a Hypothesis – Types, Examples and Writing Guide

Table of Contents

Definition:

Hypothesis is an educated guess or proposed explanation for a phenomenon, based on some initial observations or data. It is a tentative statement that can be tested and potentially proven or disproven through further investigation and experimentation.

Hypothesis is often used in scientific research to guide the design of experiments and the collection and analysis of data. It is an essential element of the scientific method, as it allows researchers to make predictions about the outcome of their experiments and to test those predictions to determine their accuracy.

Types of Hypothesis

Types of Hypothesis are as follows:

Research Hypothesis

A research hypothesis is a statement that predicts a relationship between variables. It is usually formulated as a specific statement that can be tested through research, and it is often used in scientific research to guide the design of experiments.

Null Hypothesis

The null hypothesis is a statement that assumes there is no significant difference or relationship between variables. It is often used as a starting point for testing the research hypothesis, and if the results of the study reject the null hypothesis, it suggests that there is a significant difference or relationship between variables.

Alternative Hypothesis

An alternative hypothesis is a statement that assumes there is a significant difference or relationship between variables. It is often used as an alternative to the null hypothesis and is tested against the null hypothesis to determine which statement is more accurate.

Directional Hypothesis

A directional hypothesis is a statement that predicts the direction of the relationship between variables. For example, a researcher might predict that increasing the amount of exercise will result in a decrease in body weight.

Non-directional Hypothesis

A non-directional hypothesis is a statement that predicts the relationship between variables but does not specify the direction. For example, a researcher might predict that there is a relationship between the amount of exercise and body weight, but they do not specify whether increasing or decreasing exercise will affect body weight.

Statistical Hypothesis

A statistical hypothesis is a statement that assumes a particular statistical model or distribution for the data. It is often used in statistical analysis to test the significance of a particular result.

Composite Hypothesis

A composite hypothesis is a statement that assumes more than one condition or outcome. It can be divided into several sub-hypotheses, each of which represents a different possible outcome.

Empirical Hypothesis

An empirical hypothesis is a statement that is based on observed phenomena or data. It is often used in scientific research to develop theories or models that explain the observed phenomena.

Simple Hypothesis

A simple hypothesis is a statement that assumes only one outcome or condition. It is often used in scientific research to test a single variable or factor.

Complex Hypothesis

A complex hypothesis is a statement that assumes multiple outcomes or conditions. It is often used in scientific research to test the effects of multiple variables or factors on a particular outcome.

Applications of Hypothesis

Hypotheses are used in various fields to guide research and make predictions about the outcomes of experiments or observations. Here are some examples of how hypotheses are applied in different fields:

• Science : In scientific research, hypotheses are used to test the validity of theories and models that explain natural phenomena. For example, a hypothesis might be formulated to test the effects of a particular variable on a natural system, such as the effects of climate change on an ecosystem.
• Medicine : In medical research, hypotheses are used to test the effectiveness of treatments and therapies for specific conditions. For example, a hypothesis might be formulated to test the effects of a new drug on a particular disease.
• Psychology : In psychology, hypotheses are used to test theories and models of human behavior and cognition. For example, a hypothesis might be formulated to test the effects of a particular stimulus on the brain or behavior.
• Sociology : In sociology, hypotheses are used to test theories and models of social phenomena, such as the effects of social structures or institutions on human behavior. For example, a hypothesis might be formulated to test the effects of income inequality on crime rates.
• Business : In business research, hypotheses are used to test the validity of theories and models that explain business phenomena, such as consumer behavior or market trends. For example, a hypothesis might be formulated to test the effects of a new marketing campaign on consumer buying behavior.
• Engineering : In engineering, hypotheses are used to test the effectiveness of new technologies or designs. For example, a hypothesis might be formulated to test the efficiency of a new solar panel design.

How to write a Hypothesis

Here are the steps to follow when writing a hypothesis:

Identify the Research Question

The first step is to identify the research question that you want to answer through your study. This question should be clear, specific, and focused. It should be something that can be investigated empirically and that has some relevance or significance in the field.

Conduct a Literature Review

Before writing your hypothesis, it’s essential to conduct a thorough literature review to understand what is already known about the topic. This will help you to identify the research gap and formulate a hypothesis that builds on existing knowledge.

Determine the Variables

The next step is to identify the variables involved in the research question. A variable is any characteristic or factor that can vary or change. There are two types of variables: independent and dependent. The independent variable is the one that is manipulated or changed by the researcher, while the dependent variable is the one that is measured or observed as a result of the independent variable.

Formulate the Hypothesis

Based on the research question and the variables involved, you can now formulate your hypothesis. A hypothesis should be a clear and concise statement that predicts the relationship between the variables. It should be testable through empirical research and based on existing theory or evidence.

Write the Null Hypothesis

The null hypothesis is the opposite of the alternative hypothesis, which is the hypothesis that you are testing. The null hypothesis states that there is no significant difference or relationship between the variables. It is important to write the null hypothesis because it allows you to compare your results with what would be expected by chance.

Refine the Hypothesis

After formulating the hypothesis, it’s important to refine it and make it more precise. This may involve clarifying the variables, specifying the direction of the relationship, or making the hypothesis more testable.

Examples of Hypothesis

Here are a few examples of hypotheses in different fields:

• Psychology : “Increased exposure to violent video games leads to increased aggressive behavior in adolescents.”
• Biology : “Higher levels of carbon dioxide in the atmosphere will lead to increased plant growth.”
• Sociology : “Individuals who grow up in households with higher socioeconomic status will have higher levels of education and income as adults.”
• Education : “Implementing a new teaching method will result in higher student achievement scores.”
• Marketing : “Customers who receive a personalized email will be more likely to make a purchase than those who receive a generic email.”
• Physics : “An increase in temperature will cause an increase in the volume of a gas, assuming all other variables remain constant.”
• Medicine : “Consuming a diet high in saturated fats will increase the risk of developing heart disease.”

Purpose of Hypothesis

The purpose of a hypothesis is to provide a testable explanation for an observed phenomenon or a prediction of a future outcome based on existing knowledge or theories. A hypothesis is an essential part of the scientific method and helps to guide the research process by providing a clear focus for investigation. It enables scientists to design experiments or studies to gather evidence and data that can support or refute the proposed explanation or prediction.

The formulation of a hypothesis is based on existing knowledge, observations, and theories, and it should be specific, testable, and falsifiable. A specific hypothesis helps to define the research question, which is important in the research process as it guides the selection of an appropriate research design and methodology. Testability of the hypothesis means that it can be proven or disproven through empirical data collection and analysis. Falsifiability means that the hypothesis should be formulated in such a way that it can be proven wrong if it is incorrect.

In addition to guiding the research process, the testing of hypotheses can lead to new discoveries and advancements in scientific knowledge. When a hypothesis is supported by the data, it can be used to develop new theories or models to explain the observed phenomenon. When a hypothesis is not supported by the data, it can help to refine existing theories or prompt the development of new hypotheses to explain the phenomenon.

When to use Hypothesis

Here are some common situations in which hypotheses are used:

• In scientific research , hypotheses are used to guide the design of experiments and to help researchers make predictions about the outcomes of those experiments.
• In social science research , hypotheses are used to test theories about human behavior, social relationships, and other phenomena.
• I n business , hypotheses can be used to guide decisions about marketing, product development, and other areas. For example, a hypothesis might be that a new product will sell well in a particular market, and this hypothesis can be tested through market research.

Characteristics of Hypothesis

Here are some common characteristics of a hypothesis:

• Testable : A hypothesis must be able to be tested through observation or experimentation. This means that it must be possible to collect data that will either support or refute the hypothesis.
• Falsifiable : A hypothesis must be able to be proven false if it is not supported by the data. If a hypothesis cannot be falsified, then it is not a scientific hypothesis.
• Clear and concise : A hypothesis should be stated in a clear and concise manner so that it can be easily understood and tested.
• Based on existing knowledge : A hypothesis should be based on existing knowledge and research in the field. It should not be based on personal beliefs or opinions.
• Specific : A hypothesis should be specific in terms of the variables being tested and the predicted outcome. This will help to ensure that the research is focused and well-designed.
• Tentative: A hypothesis is a tentative statement or assumption that requires further testing and evidence to be confirmed or refuted. It is not a final conclusion or assertion.
• Relevant : A hypothesis should be relevant to the research question or problem being studied. It should address a gap in knowledge or provide a new perspective on the issue.

Advantages of Hypothesis

Hypotheses have several advantages in scientific research and experimentation:

• Guides research: A hypothesis provides a clear and specific direction for research. It helps to focus the research question, select appropriate methods and variables, and interpret the results.
• Predictive powe r: A hypothesis makes predictions about the outcome of research, which can be tested through experimentation. This allows researchers to evaluate the validity of the hypothesis and make new discoveries.
• Facilitates communication: A hypothesis provides a common language and framework for scientists to communicate with one another about their research. This helps to facilitate the exchange of ideas and promotes collaboration.
• Efficient use of resources: A hypothesis helps researchers to use their time, resources, and funding efficiently by directing them towards specific research questions and methods that are most likely to yield results.
• Provides a basis for further research: A hypothesis that is supported by data provides a basis for further research and exploration. It can lead to new hypotheses, theories, and discoveries.
• Increases objectivity: A hypothesis can help to increase objectivity in research by providing a clear and specific framework for testing and interpreting results. This can reduce bias and increase the reliability of research findings.

Limitations of Hypothesis

Some Limitations of the Hypothesis are as follows:

• Limited to observable phenomena: Hypotheses are limited to observable phenomena and cannot account for unobservable or intangible factors. This means that some research questions may not be amenable to hypothesis testing.
• May be inaccurate or incomplete: Hypotheses are based on existing knowledge and research, which may be incomplete or inaccurate. This can lead to flawed hypotheses and erroneous conclusions.
• May be biased: Hypotheses may be biased by the researcher’s own beliefs, values, or assumptions. This can lead to selective interpretation of data and a lack of objectivity in research.
• Cannot prove causation: A hypothesis can only show a correlation between variables, but it cannot prove causation. This requires further experimentation and analysis.
• Limited to specific contexts: Hypotheses are limited to specific contexts and may not be generalizable to other situations or populations. This means that results may not be applicable in other contexts or may require further testing.
• May be affected by chance : Hypotheses may be affected by chance or random variation, which can obscure or distort the true relationship between variables.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

You may also like

Research Topics – Ideas and Examples

Informed Consent in Research – Types, Templates...

Figures in Research Paper – Examples and Guide

Research Problem – Examples, Types and Guide

APA Table of Contents – Format and Example

Conceptual Framework – Types, Methodology and...

• Dictionaries home
• American English
• Collocations
• German-English
• Grammar home
• Practical English Usage
• Learn & Practise Grammar (Beta)
• Word Lists home
• My Word Lists
• Recent additions
• Resources home
• Text Checker

Definition of hypothesis noun from the Oxford Advanced Learner's Dictionary

• to formulate/confirm a hypothesis
• a hypothesis about the function of dreams
• There is little evidence to support these hypotheses.
• formulate/​advance a theory/​hypothesis
• build/​construct/​create/​develop a simple/​theoretical/​mathematical model
• develop/​establish/​provide/​use a theoretical/​conceptual framework
• advance/​argue/​develop the thesis that…
• explore an idea/​a concept/​a hypothesis
• make a prediction/​an inference
• base a prediction/​your calculations on something
• investigate/​evaluate/​accept/​challenge/​reject a theory/​hypothesis/​model
• design an experiment/​a questionnaire/​a study/​a test
• do research/​an experiment/​an analysis
• make observations/​measurements/​calculations
• carry out/​conduct/​perform an experiment/​a test/​a longitudinal study/​observations/​clinical trials
• run an experiment/​a simulation/​clinical trials
• repeat an experiment/​a test/​an analysis
• replicate a study/​the results/​the findings
• observe/​study/​examine/​investigate/​assess a pattern/​a process/​a behaviour
• fund/​support the research/​project/​study
• seek/​provide/​get/​secure funding for research
• collect/​gather/​extract data/​information
• yield data/​evidence/​similar findings/​the same results
• analyse/​examine the data/​soil samples/​a specimen
• consider/​compare/​interpret the results/​findings
• fit the data/​model
• confirm/​support/​verify a prediction/​a hypothesis/​the results/​the findings
• prove a conjecture/​hypothesis/​theorem
• draw/​make/​reach the same conclusions
• read/​review the records/​literature
• describe/​report an experiment/​a study
• present/​publish/​summarize the results/​findings
• present/​publish/​read/​review/​cite a paper in a scientific journal
• Her hypothesis concerns the role of electromagnetic radiation.
• Her study is based on the hypothesis that language simplification is possible.
• It is possible to make a hypothesis on the basis of this graph.
• None of the hypotheses can be rejected at this stage.
• Scientists have proposed a bold hypothesis.
• She used this data to test her hypothesis
• The hypothesis predicts that children will perform better on task A than on task B.
• The results confirmed his hypothesis on the use of modal verbs.
• These observations appear to support our working hypothesis.
• a speculative hypothesis concerning the nature of matter
• an interesting hypothesis about the development of language
• Advances in genetics seem to confirm these hypotheses.
• His hypothesis about what dreams mean provoked a lot of debate.
• Research supports the hypothesis that language skills are centred in the left side of the brain.
• The survey will be used to test the hypothesis that people who work outside the home are fitter and happier.
• This economic model is really a working hypothesis.
• speculative
• concern something
• be based on something
• predict something
• on a/​the hypothesis
• hypothesis about
• hypothesis concerning

Join our community to access the latest language learning and assessment tips from Oxford University Press!

• It would be pointless to engage in hypothesis before we have the facts.

Other results

Nearby words.

• The STEM Crisis & Our Solution
• Massachusetts
• Our Supporters
• Description
• School Partners
• Vacation Programs
• Community Outreach
• Homeschool STEM Workshops
• SciSci In The Field
• Growing the Future at EPCOT®
• ACCESS Program
• Teacher Resources
• Family Resources
• Donate to Us
• Join our Team
• Volunteer Opportunities

What is a Hypothesis?

Experimental Design

Today, students learned about the importance of experimental design. Starting with the steps of the Ruler Drop Experiment which we can use to test reaction times, students came up with their own hypotheses about what variables might affect people’s reaction times. Then they came up with their own experimental plans to test these hypotheses. Students learned that it is important that a good hypothesis makes a claim about the relationship between two variables, and that this relationship is specific and testable in a measurable way. Students also learned that only one variable—the independent variable—can differ between test groups. Finally, we talked about how it is important to have more than one test subject so that an average can be taken. Ask your student to test your reaction times!

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

This site uses Akismet to reduce spam. Learn how your comment data is processed .

• News and Events

Latest Posts

Job applications.

[email protected]

533 Airport Blvd, Suite 135 Burlingame, CA 94010

MASSACHUSETTS

16 Tower Office Park Woburn, MA 01801

9001 E Bloomington Fwy, Suite #139 Bloomington MN 55420

FOR FAMILIES

For teachers.

Copyright © 2014 - 2022 Science From Scientists - All rights reserved.

Website by Modern Leaf Design

All Subjects

Intro to Sociology

A hypothesis is an educated guess or proposition that attempts to explain a set of facts or phenomena in sociology. It is a testable statement that can be supported or refuted through empirical research and observation.

Related terms

Empirical Research : The collection and analysis of data from the real world to evaluate the validity of a hypothesis.

Sociological Theory : A framework or system of ideas that helps to explain social phenomena, often forming the basis for generating hypotheses.

Variable : An element, feature, or factor that is liable to vary or change, which researchers manipulate or measure in their studies to assess the effects on another variable

" Hypothesis " appears in:

Study guides ( 1 ).

• Intro to Sociology - 1.3 Theoretical Perspectives in Sociology

Subjects ( 36 )

• AP Art & Design
• AP Human Geography
• AP Psychology
• AP Research
• College Biology
• College Introductory Statistics
• College Physics: Mechanics, Sound, Oscillations, and Waves
• Concepts of Biology for Non-Science Majors
• Contemporary Mathematics for Non-Math Majors
• Critical Thinking
• Customer Insights
• Early Modern Europe, 1450-1750
• Feature Writing
• Foundations of Lower Division Mathematics
• History of Science
• Honors Biology
• Honors Geometry
• Honors Physics
• Honors Statistics
• Intro to Astronomy
• Intro to Chemistry
• Intro to Political Science
• Intro to Psychology
• Introduction to Aristotle
• Introduction to Environmental Science
• Introduction to Geology
• Introduction to News Reporting
• Journalism Research
• Philosophy of Science
• Physical Science
• Principles of Physics I
• Professionalism and Research in Nursing
• Reporting in Depth
• Rescuing Lost Stories
• Science Education

© 2024 Fiveable Inc. All rights reserved.

Ap® and sat® are trademarks registered by the college board, which is not affiliated with, and does not endorse this website..

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Microb Biotechnol
• v.15(11); 2022 Nov

On the role of hypotheses in science

Harald brüssow.

1 Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Leuven Belgium

Associated Data

Scientific research progresses by the dialectic dialogue between hypothesis building and the experimental testing of these hypotheses. Microbiologists as biologists in general can rely on an increasing set of sophisticated experimental methods for hypothesis testing such that many scientists maintain that progress in biology essentially comes with new experimental tools. While this is certainly true, the importance of hypothesis building in science should not be neglected. Some scientists rely on intuition for hypothesis building. However, there is also a large body of philosophical thinking on hypothesis building whose knowledge may be of use to young scientists. The present essay presents a primer into philosophical thoughts on hypothesis building and illustrates it with two hypotheses that played a major role in the history of science (the parallel axiom and the fifth element hypothesis). It continues with philosophical concepts on hypotheses as a calculus that fits observations (Copernicus), the need for plausibility (Descartes and Gilbert) and for explicatory power imposing a strong selection on theories (Darwin, James and Dewey). Galilei introduced and James and Poincaré later justified the reductionist principle in hypothesis building. Waddington stressed the feed‐forward aspect of fruitful hypothesis building, while Poincaré called for a dialogue between experiment and hypothesis and distinguished false, true, fruitful and dangerous hypotheses. Theoretical biology plays a much lesser role than theoretical physics because physical thinking strives for unification principle across the universe while biology is confronted with a breathtaking diversity of life forms and its historical development on a single planet. Knowledge of the philosophical foundations on hypothesis building in science might stimulate more hypothesis‐driven experimentation that simple observation‐oriented “fishing expeditions” in biological research.

Short abstract

Scientific research progresses by the dialectic dialogue between hypothesis building and the experimental testing of these hypotheses. Microbiologists can rely on an increasing set of sophisticated experimental methods for hypothesis testing but the importance of hypothesis building in science should not be neglected. This Lilliput offers a primer on philosophical concepts on hypotheses in science.

INTRODUCTION

Philosophy of science and the theory of knowledge (epistemology) are important branches of philosophy. However, philosophy has over the centuries lost its dominant role it enjoyed in antiquity and became in Medieval Ages the maid of theology (ancilla theologiae) and after the rise of natural sciences and its technological applications many practising scientists and the general public doubt whether they need philosophical concepts in their professional and private life. This is in the opinion of the writer of this article, an applied microbiologist, shortsighted for several reasons. Philosophers of the 20th century have made important contributions to the theory of knowledge, and many eminent scientists grew interested in philosophical problems. Mathematics which plays such a prominent role in physics and increasingly also in other branches of science is a hybrid: to some extent, it is the paradigm of an exact science while its abstract aspects are deeply rooted in philosophical thinking. In the present essay, the focus is on hypothesis and hypothesis building in science, essentially it is a compilation what philosophers and scientists thought about this subject in past and present. The controversy between the mathematical mind and that of the practical mind is an old one. The philosopher, physicist and mathematician Pascal ( 1623 –1662a) wrote in his Pensées : “Mathematicians who are only mathematicians have exact minds, provided all things are explained to them by means of definitions and axioms; otherwise they are inaccurate. They are only right when the principles are quite clear. And men of intuition cannot have the patience to reach to first principles of things speculative and conceptional, which they have never seen in the world and which are altogether out of the common. The intellect can be strong and narrow, and can be comprehensive and weak.” Hypothesis building is an act both of intuition and exact thinking and I hope that theoretical knowledge about hypothesis building will also profit young microbiologists.

HYPOTHESES AND AXIOMS IN MATHEMATICS

In the following, I will illustrate the importance of hypothesis building for the history of science and the development of knowledge and illustrate it with two famous concepts, the parallel axiom in mathematics and the five elements hypothesis in physics.

Euclidean geometry

The prominent role of hypotheses in the development of science becomes already clear in the first science book of the Western civilization: Euclid's The Elements written about 300 BC starts with a set of statements called Definitions, Postulates and Common Notions that lay out the foundation of geometry (Euclid,  c.323‐c.283 ). This axiomatic approach is very modern as exemplified by the fact that Euclid's book remained for long time after the Bible the most read book in the Western hemisphere and a backbone of school teaching in mathematics. Euclid's twenty‐three definitions start with sentences such as “1. A point is that which has no part; 2. A line is breadthless length; 3. The extremities of a line are points”; and continues with the definition of angles (“8. A plane angle is the inclination to one another of two lines in a plane which meet one another and do not lie in a straight line”) and that of circles, triangles and quadrilateral figures. For the history of science, the 23rd definition of parallels is particularly interesting: “Parallel straight lines are straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction”. This is the famous parallel axiom. It is clear that the parallel axiom cannot be the result of experimental observations, but must be a concept created in the mind. Euclid ends with five Common Notions (“1. Things which are equal to the same thing are also equal to one another, to 5. The whole is greater than the part”). The establishment of a contradiction‐free system for a branch of mathematics based on a set of axioms from which theorems were deduced was revolutionary modern. Hilbert ( 1899 ) formulated a sound modern formulation for Euclidian geometry. Hilbert's axiom system contains the notions “point, line and plane” and the concepts of “betweenness, containment and congruence” leading to five axioms, namely the axioms of Incidence (“Verknüpfung”), of Order (“Anordnung”), of Congruence, of Continuity (“Stetigkeit”) and of Parallels.

Origin of axioms

Philosophers gave various explanations for the origin of the Euclidean hypotheses or axioms. Plato considered geometrical figures as related to ideas (the true things behind the world of appearances). Aristoteles considered geometric figures as abstractions of physical bodies. Descartes perceived geometric figures as inborn ideas from extended bodies ( res extensa ), while Pascal thought that the axioms of Euclidian geometry were derived from intuition. Kant reasoned that Euclidian geometry represented a priori perceptions of space. Newton considered geometry as part of general mechanics linked to theories of measurement. Hilbert argued that the axioms of mathematical geometry are neither the result of contemplation (“Anschauung”) nor of psychological source. For him, axioms were formal propositions (“formale Aussageformen”) characterized by consistency (“Widerspruchsfreiheit”, i.e. absence of contradiction) (Mittelstrass,  1980a ).

Definitions

Axioms were also differently defined by philosophers. In Topics , Aristoteles calls axioms the assumptions taken up by one partner of a dialogue to initiate a dialectic discussion. Plato states that an axiom needs to be an acceptable or credible proposition, which cannot be justified by reference to other statements. Yet, a justification is not necessary because an axiom is an evident statement. In modern definition, axioms are methodical first sentences in the foundation of a deductive science (Mittelstrass,  1980a ). In Posterior Analytics , Aristotle defines postulates as positions which are at least initially not accepted by the dialogue partners while hypotheses are accepted for the sake of reasoning. In Euclid's book, postulates are construction methods that assure the existence of the geometric objects. Today postulates and axioms are used as synonyms while the 18th‐century philosophy made differences: Lambert defined axioms as descriptive sentences and postulates as prescriptive sentences. According to Kant, mathematical postulates create (synthesize) concepts (Mittelstrass,  1980b ). Definitions then fix the use of signs; they can be semantic definitions that explain the proper meaning of a sign in common language use (in a dictionary style) or they can be syntactic definitions that regulate the use of these signs in formal operations. Nominal definitions explain the words, while real definitions explain the meaning or the nature of the defined object. Definitions are thus essential for the development of a language of science, assuring communication and mutual understanding (Mittelstrass,  1980c ). Finally, hypotheses are also frequently defined as consistent conjectures that are compatible with the available knowledge. The truth of the hypothesis is only supposed in order to explain true observations and facts. Consequences of this hypothetical assumptions should explain the observed facts. Normally, descriptive hypotheses precede explanatory hypotheses in the development of scientific thought. Sometimes only tentative concepts are introduced as working hypotheses to test whether they have an explanatory capacity for the observations (Mittelstrass,  1980d ).

The Euclidian geometry is constructed along a logical “if→then” concept. The “if‐clause” formulates at the beginning the supposition, the “then clause” formulates the consequences from these axioms which provides a system of geometric theorems or insights. The conclusions do not follow directly from the hypothesis; this would otherwise represent self‐evident immediate conclusions. The “if‐then” concept in geometry is not used as in other branches of science where the consequences deduced from the axioms are checked against reality whether they are true, in order to confirm the validity of the hypothesis. The task in mathematics is: what can be logically deduced from a given set of axioms to build a contradiction‐free system of geometry. Whether this applies to the real world is in contrast to the situation in natural sciences another question and absolutely secondary to mathematics (Syntopicon,  1992 ).

Pascal's rules for hypotheses

In his Scientific Treatises on Geometric Demonstrations , Pascal ( 1623‐1662b ) formulates “Five rules are absolutely necessary and we cannot dispense with them without an essential defect and frequently even error. Do not leave undefined any terms at all obscure or ambiguous. Use in definitions of terms only words perfectly well known or already explained. Do not fail to ask that each of the necessary principles be granted, however clear and evident it may be. Ask only that perfectly self‐evident things be granted as axioms. Prove all propositions, using for their proof only axioms that are perfectly self‐evident or propositions already demonstrated or granted. Never get caught in the ambiguity of terms by failing to substitute in thought the definitions which restrict or define them. One should accept as true only those things whose contradiction appears to be false. We may then boldly affirm the original statement, however incomprehensible it is.”

Kant's rules on hypotheses

Kant ( 1724–1804 ) wrote that the analysis described in his book The Critique of Pure Reason “has now taught us that all its efforts to extend the bounds of knowledge by means of pure speculation, are utterly fruitless. So much the wider field lies open to hypothesis; as where we cannot know with certainty, we are at liberty to make guesses and to form suppositions. Imagination may be allowed, under the strict surveillance of reason, to invent suppositions; but these must be based on something that is perfectly certain‐ and that is the possibility of the object. Such a supposition is termed a hypothesis. We cannot imagine or invent any object or any property of an object not given in experience and employ it in a hypothesis; otherwise we should be basing our chain of reasoning upon mere chimerical fancies and not upon conception of things. Thus, we have no right to assume of new powers, not existing in nature and consequently we cannot assume that there is any other kind of community among substances than that observable in experience, any kind of presence than that in space and any kind of duration than that in time. The conditions of possible experience are for reason the only conditions of the possibility of things. Otherwise, such conceptions, although not self‐contradictory, are without object and without application. Transcendental hypotheses are therefore inadmissible, and we cannot use the liberty of employing in the absence of physical, hyperphysical grounds of explanation because such hypotheses do not advance reason, but rather stop it in its progress. When the explanation of natural phenomena happens to be difficult, we have constantly at hand a transcendental ground of explanation, which lifts us above the necessity of investigating nature. The next requisite for the admissibility of a hypothesis is its sufficiency. That is it must determine a priori the consequences which are given in experience and which are supposed to follow from the hypothesis itself.” Kant stresses another aspect when dealing with hypotheses: “It is our duty to try to discover new objections, to put weapons in the hands of our opponent, and to grant him the most favorable position. We have nothing to fear from these concessions; on the contrary, we may rather hope that we shall thus make ourselves master of a possession which no one will ever venture to dispute.”

For Kant's analytical and synthetical judgements and Difference between philosophy and mathematics (Kant, Whitehead) , see Appendices  S1 and S2 , respectively.

Poincaré on hypotheses

The mathematician‐philosopher Poincaré ( 1854 –1912a) explored the foundation of mathematics and physics in his book Science and Hypothesis . In the preface to the book, he summarizes common thinking of scientists at the end of the 19th century. “To the superficial observer scientific truth is unassailable, the logic of science is infallible, and if scientific men sometimes make mistakes, it is because they have not understood the rules of the game. Mathematical truths are derived from a few self‐evident propositions, by a chain of flawless reasoning, they are imposed not only by us, but on Nature itself. This is for the minds of most people the origin of certainty in science.” Poincaré then continues “but upon more mature reflection the position held by hypothesis was seen; it was recognized that it is as necessary to the experimenter as it is to the mathematician. And then the doubt arose if all these constructions are built on solid foundations.” However, “to doubt everything or to believe everything are two equally convenient solutions: both dispense with the necessity of reflection. Instead, we should examine with the utmost care the role of hypothesis; we shall then recognize not only that it is necessary, but that in most cases it is legitimate. We shall also see that there are several kinds of hypotheses; that some are verifiable and when once confirmed by experiment become truths of great fertility; that others may be useful to us in fixing our ideas; and finally that others are hypotheses only in appearance, and reduce to definitions or to conventions in disguise.” Poincaré argues that “we must seek mathematical thought where it has remained pure‐i.e. in arithmetic, in the proofs of the most elementary theorems. The process is proof by recurrence. We first show that a theorem is true for n  = 1; we then show that if it is true for n –1 it is true for n; and we conclude that it is true for all integers. The essential characteristic of reasoning by recurrence is that it contains, condensed in a single formula, an infinite number of syllogisms.” Syllogism is logical argument that applies deductive reasoning to arrive at a conclusion. Poincaré notes “that here is a striking analogy with the usual process of induction. But an essential difference exists. Induction applied to the physical sciences is always uncertain because it is based on the belief in a general order of the universe, an order which is external to us. Mathematical induction‐ i.e. proof by recurrence – is on the contrary, necessarily imposed on us, because it is only the affirmation of a property of the mind itself. No doubt mathematical recurrent reasoning and physical inductive reasoning are based on different foundations, but they move in parallel lines and in the same direction‐namely, from the particular to the general.”

Non‐Euclidian geometry: from Gauss to Lobatschewsky

Mathematics is an abstract science that intrinsically does not request that the structures described reflect a physical reality. Paradoxically, mathematics is the language of physics since the founder of experimental physics Galilei used Euclidian geometry when exploring the laws of the free fall. In his 1623 treatise The Assayer , Galilei ( 1564 –1642a) famously formulated that the book of Nature is written in the language of mathematics, thus establishing a link between formal concepts in mathematics and the structure of the physical world. Euclid's parallel axiom played historically a prominent role for the connection between mathematical concepts and physical realities. Mathematicians had doubted that the parallel axiom was needed and tried to prove it. In Euclidian geometry, there is a connection between the parallel axiom and the sum of the angles in a triangle being two right angles. It is therefore revealing that the famous mathematician C.F. Gauss investigated in the early 19th century experimentally whether this Euclidian theorem applies in nature. He approached this problem by measuring the sum of angles in a real triangle by using geodetic angle measurements of three geographical elevations in the vicinity of Göttingen where he was teaching mathematics. He reportedly measured a sum of the angles in this triangle that differed from 180°. Gauss had at the same time also developed statistical methods to evaluate the accuracy of measurements. Apparently, the difference of his measured angles was still within the interval of Gaussian error propagation. He did not publish the reasoning and the results for this experiment because he feared the outcry of colleagues about this unorthodox, even heretical approach to mathematical reasoning (Carnap,  1891 ‐1970a). However, soon afterwards non‐Euclidian geometries were developed. In the words of Poincaré, “Lobatschewsky assumes at the outset that several parallels may be drawn through a point to a given straight line, and he retains all the other axioms of Euclid. From these hypotheses he deduces a series of theorems between which it is impossible to find any contradiction, and he constructs a geometry as impeccable in its logic as Euclidian geometry. The theorems are very different, however, from those to which we are accustomed, and at first will be found a little disconcerting. For instance, the sum of the angles of a triangle is always less than two right angles, and the difference between that sum and two right angles is proportional to the area of the triangle. Lobatschewsky's propositions have no relation to those of Euclid, but are none the less logically interconnected.” Poincaré continues “most mathematicians regard Lobatschewsky's geometry as a mere logical curiosity. Some of them have, however, gone further. If several geometries are possible, they say, is it certain that our geometry is true? Experiments no doubt teaches us that the sum of the angles of a triangle is equal to two right angles, but this is because the triangles we deal with are too small” (Poincaré,  1854 ‐1912a)—hence the importance of Gauss' geodetic triangulation experiment. Gauss was aware that his three hills experiment was too small and thought on measurements on triangles formed with stars.

Poincaré vs. Einstein

Lobatschewsky's hyperbolic geometry did not remain the only non‐Euclidian geometry. Riemann developed a geometry without the parallel axiom, while the other Euclidian axioms were maintained with the exception of that of Order (Anordnung). Poincaré notes “so there is a kind of opposition between the geometries. For instance the sum of the angles in a triangle is equal to two right angles in Euclid's geometry, less than two right angles in that of Lobatschewsky, and greater than two right angles in that of Riemann. The number of parallel lines that can be drawn through a given point to a given line is one in Euclid's geometry, none in Riemann's, and an infinite number in the geometry of Lobatschewsky. Let us add that Riemann's space is finite, although unbounded.” As further distinction, the ratio of the circumference to the diameter of a circle is equal to π in Euclid's, greater than π in Lobatschewsky's and smaller than π in Riemann's geometry. A further difference between these geometries concerns the degree of curvature (Krümmungsmass k) which is 0 for a Euclidian surface, smaller than 0 for a Lobatschewsky and greater than 0 for a Riemann surface. The difference in curvature can be roughly compared with plane, concave and convex surfaces. The inner geometric structure of a Riemann plane resembles the surface structure of a Euclidean sphere and a Lobatschewsky plane resembles that of a Euclidean pseudosphere (a negatively curved geometry of a saddle). What geometry is true? Poincaré asked “Ought we then, to conclude that the axioms of geometry are experimental truths?” and continues “If geometry were an experimental science, it would not be an exact science. The geometric axioms are therefore neither synthetic a priori intuitions as affirmed by Kant nor experimental facts. They are conventions. Our choice among all possible conventions is guided by experimental facts; but it remains free and is only limited by the necessity of avoiding contradictions. In other words, the axioms of geometry are only definitions in disguise. What then are we to think of the question: Is Euclidean geometry true? It has no meaning. One geometry cannot be more true than another, it can only be more convenient. Now, Euclidean geometry is, and will remain, the most convenient, 1 st because it is the simplest and 2 nd because it sufficiently agrees with the properties of natural bodies” (Poincaré,  1854 ‐1912a).

Poincaré's book was published in 1903 and only a few years later Einstein published his general theory of relativity ( 1916 ) where he used a non‐Euclidean, Riemann geometry and where he demonstrated a structure of space that deviated from Euclidean geometry in the vicinity of strong gravitational fields. And in 1919, astronomical observations during a solar eclipse showed that light rays from a distant star were indeed “bent” when passing next to the sun. These physical observations challenged the view of Poincaré, and we should now address some aspects of hypotheses in physics (Carnap,  1891 ‐1970b).

HYPOTHESES IN PHYSICS

The long life of the five elements hypothesis.

Physical sciences—not to speak of biological sciences — were less developed in antiquity than mathematics which is already demonstrated by the primitive ideas on the elements constituting physical bodies. Plato and Aristotle spoke of the four elements which they took over from Thales (water), Anaximenes (air) and Parmenides (fire and earth) and add a fifth element (quinta essentia, our quintessence), namely ether. Ether is imagined a heavenly element belonging to the supralunar world. In Plato's dialogue Timaios (Plato,  c.424‐c.348 BC a ), the five elements were associated with regular polyhedra in geometry and became known as Platonic bodies: tetrahedron (fire), octahedron (air), cube (earth), icosahedron (water) and dodecahedron (ether). In regular polyhedra, faces are congruent (identical in shape and size), all angles and all edges are congruent, and the same number of faces meet at each vertex. The number of elements is limited to five because in Euclidian space there are exactly five regular polyhedral. There is in Plato's writing even a kind of geometrical chemistry. Since two octahedra (air) plus one tetrahedron (fire) can be combined into one icosahedron (water), these “liquid” elements can combine while this is not the case for combinations with the cube (earth). The 12 faces of the dodecahedron were compared with the 12 zodiac signs (Mittelstrass,  1980e ). This geometry‐based hypothesis of physics had a long life. As late as 1612, Kepler in his Mysterium cosmographicum tried to fit the Platonic bodies into the planetary shells of his solar system model. The ether theory even survived into the scientific discussion of the 19th‐century physics and the idea of a mathematical structure of the universe dominated by symmetry operations even fertilized 20th‐century ideas about symmetry concepts in the physics of elementary particles.

Huygens on sound waves in air

The ether hypothesis figures prominently in the 1690 Treatise on Light from Huygens ( 1617‐1670 ). He first reports on the transmission of sound by air when writing “this may be proved by shutting up a sounding body in a glass vessel from which the air is withdrawn and care was taken to place the sounding body on cotton that it cannot communicate its tremor to the glass vessel which encloses it. After having exhausted all the air, one hears no sound from the metal though it is struck.” Huygens comes up with some foresight when suspecting “the air is of such a nature that it can be compressed and reduced to a much smaller space than that it normally occupies. Air is made up of small bodies which float about and which are agitated very rapidly. So that the spreading of sound is the effort which these little bodies make in collisions with one another, to regain freedom when they are a little more squeezed together in the circuit of these waves than elsewhere.”

Huygens on light waves in ether

“That is not the same air but another kind of matter in which light spreads; since if the air is removed from the vessel the light does not cease to traverse it as before. The extreme velocity of light cannot admit such a propagation of motion” as sound waves. To achieve the propagation of light, Huygens invokes ether “as a substance approaching to perfect hardness and possessing springiness as prompt as we choose. One may conceive light to spread successively by spherical waves. The propagation consists nowise in the transport of those particles but merely in a small agitation which they cannot help communicate to those surrounding.” The hypothesis of an ether in outer space fills libraries of physical discussions, but all experimental approaches led to contradictions with respect to postulated properties of this hypothetical material for example when optical experiments showed that light waves display transversal and not longitudinal oscillations.

The demise of ether

Mechanical models for the transmission of light or gravitation waves requiring ether were finally put to rest by the theory of relativity from Einstein (Mittelstrass,  1980f ). This theory posits that the speed of light in an empty space is constant and does not depend on movements of the source of light or that of an observer as requested by the ether hypothesis. The theory of relativity also provides an answer how the force of gravitation is transmitted from one mass to another across an essentially empty space. In the non‐Euclidian formulation of the theory of relativity (Einstein used the Riemann geometry), there is no gravitation force in the sense of mechanical or electromagnetic forces. The gravitation force is in this formulation simply replaced by a geometric structure (space curvature near high and dense masses) of a four‐dimensional space–time system (Carnap,  1891 ‐1970c; Einstein & Imfeld,  1956 ) Gravitation waves and gravitation lens effects have indeed been experimental demonstrated by astrophysicists (Dorfmüller et al.,  1998 ).

For Aristotle's on physical hypotheses , see Appendix  S3 .

PHILOSOPHICAL THOUGHTS ON HYPOTHESES

In the following, the opinions of a number of famous scientists and philosophers on hypotheses are quoted to provide a historical overview on the subject.

Copernicus' hypothesis: a calculus which fits observations

In his book Revolutions of Heavenly Spheres Copernicus ( 1473–1543 ) reasoned in the preface about hypotheses in physics. “Since the newness of the hypotheses of this work ‐which sets the earth in motion and puts an immovable sun at the center of the universe‐ has already received a great deal of publicity, I have no doubt that certain of the savants have taken great offense.” He defended his heliocentric thesis by stating “For it is the job of the astronomer to use painstaking and skilled observations in gathering together the history of the celestial movements‐ and then – since he cannot by any line of reasoning reach the true causes of these movements‐ to think up or construct whatever causes or hypotheses he pleases such that, by the assumption of these causes, those same movements can be calculated from the principles of geometry for the past and the future too. This artist is markedly outstanding in both of these respects: for it is not necessary that these hypotheses should be true, or even probable; but it is enough if they provide a calculus which fits the observations.” This preface written in 1543 sounds in its arguments very modern physics. However, historians of science have discovered that it was probably written by a theologian friend of Copernicus to defend the book against the criticism by the church.

Bacon's intermediate hypotheses

In his book Novum Organum , Francis Bacon ( 1561–1626 ) claims for hypotheses and scientific reasoning “that they augur well for the sciences, when the ascent shall proceed by a true scale and successive steps, without interruption or breach, from particulars to the lesser axioms, thence to the intermediates and lastly to the most general.” He then notes “that the lowest axioms differ but little from bare experiments, the highest and most general are notional, abstract, and of no real weight. The intermediate are true, solid, full of life, and up to them depend the business and fortune of mankind.” He warns that “we must not then add wings, but rather lead and ballast to the understanding, to prevent its jumping and flying, which has not yet been done; but whenever this takes place we may entertain greater hopes of the sciences.” With respect to methodology, Bacon claims that “we must invent a different form of induction. The induction which proceeds by simple enumeration is puerile, leads to uncertain conclusions, …deciding generally from too small a number of facts. Sciences should separate nature by proper rejections and exclusions and then conclude for the affirmative, after collecting a sufficient number of negatives.”

Gilbert and Descartes for plausible hypotheses

William Gilbert introduced in his book On the Loadstone (Gilbert,  1544‐1603 ) the argument of plausibility into physical hypothesis building. “From these arguments, therefore, we infer not with mere probability, but with certainty, the diurnal rotation of the earth; for nature ever acts with fewer than with many means; and because it is more accordant to reason that the one small body, the earth, should make a daily revolution than the whole universe should be whirled around it.”

Descartes ( 1596‐1650 ) reflected on the sources of understanding in his book Rules for Direction and distinguished what “comes about by impulse, by conjecture, or by deduction. Impulse can assign no reason for their belief and when determined by fanciful disposition, it is almost always a source of error.” When speaking about the working of conjectures he quotes thoughts of Aristotle: “water which is at a greater distance from the center of the globe than earth is likewise less dense substance, and likewise the air which is above the water, is still rarer. Hence, we hazard the guess that above the air nothing exists but a very pure ether which is much rarer than air itself. Moreover nothing that we construct in this way really deceives, if we merely judge it to be probable and never affirm it to be true; in fact it makes us better instructed. Deduction is thus left to us as the only means of putting things together so as to be sure of their truth. Yet in it, too, there may be many defects.”

Care in formulating hypotheses

Locke ( 1632‐1704 ) in his treatise Concerning Human Understanding admits that “we may make use of any probable hypotheses whatsoever. Hypotheses if they are well made are at least great helps to the memory and often direct us to new discoveries. However, we should not take up any one too hastily.” Also, practising scientists argued against careless use of hypotheses and proposed remedies. Lavoisier ( 1743‐1794 ) in the preface to his Element of Chemistry warned about beaten‐track hypotheses. “Instead of applying observation to the things we wished to know, we have chosen rather to imagine them. Advancing from one ill‐founded supposition to another, we have at last bewildered ourselves amidst a multitude of errors. These errors becoming prejudices, are adopted as principles and we thus bewilder ourselves more and more. We abuse words which we do not understand. There is but one remedy: this is to forget all that we have learned, to trace back our ideas to their sources and as Bacon says to frame the human understanding anew.”

Faraday ( 1791–1867 ) in a Speculation Touching Electric Conduction and the Nature of Matter highlighted the fundamental difference between hypotheses and facts when noting “that he has most power of penetrating the secrets of nature, and guessing by hypothesis at her mode of working, will also be most careful for his own safe progress and that of others, to distinguish that knowledge which consists of assumption, by which I mean theory and hypothesis, from that which is the knowledge of facts and laws; never raising the former to the dignity or authority of the latter.”

Explicatory power justifies hypotheses

Darwin ( 1809 –1882a) defended the conclusions and hypothesis of his book The Origin of Species “that species have been modified in a long course of descent. This has been affected chiefly through the natural selection of numerous, slight, favorable variations.” He uses a post hoc argument for this hypothesis: “It can hardly be supposed that a false theory would explain, to so satisfactory a manner as does the theory of natural selection, the several large classes of facts” described in his book.

The natural selection of hypotheses

In the concluding chapter of The Descent of Man Darwin ( 1809 –1882b) admits “that many of the views which have been advanced in this book are highly speculative and some no doubt will prove erroneous.” However, he distinguished that “false facts are highly injurious to the progress of science for they often endure long; but false views do little harm for everyone takes a salutory pleasure in proving their falseness; and when this is done, one path to error is closed and the road to truth is often at the same time opened.”

The American philosopher William James ( 1842–1907 ) concurred with Darwin's view when he wrote in his Principles of Psychology “every scientific conception is in the first instance a spontaneous variation in someone'’s brain. For one that proves useful and applicable there are a thousand that perish through their worthlessness. The scientific conceptions must prove their worth by being verified. This test, however, is the cause of their preservation, not of their production.”

The American philosopher J. Dewey ( 1859‐1952 ) in his treatise Experience and Education notes that “the experimental method of science attaches more importance not less to ideas than do other methods. There is no such thing as experiment in the scientific sense unless action is directed by some leading idea. The fact that the ideas employed are hypotheses, not final truths, is the reason why ideas are more jealously guarded and tested in science than anywhere else. As fixed truths they must be accepted and that is the end of the matter. But as hypotheses, they must be continuously tested and revised, a requirement that demands they be accurately formulated. Ideas or hypotheses are tested by the consequences which they produce when they are acted upon. The method of intelligence manifested in the experimental method demands keeping track of ideas, activities, and observed consequences. Keeping track is a matter of reflective review.”

The reductionist principle

James ( 1842‐1907 ) pushed this idea further when saying “Scientific thought goes by selection. We break the solid plenitude of fact into separate essences, conceive generally what only exists particularly, and by our classifications leave nothing in its natural neighborhood. The reality exists as a plenum. All its part are contemporaneous, but we can neither experience nor think this plenum. What we experience is a chaos of fragmentary impressions, what we think is an abstract system of hypothetical data and laws. We must decompose each chaos into single facts. We must learn to see in the chaotic antecedent a multitude of distinct antecedents, in the chaotic consequent a multitude of distinct consequents.” From these considerations James concluded “even those experiences which are used to prove a scientific truth are for the most part artificial experiences of the laboratory gained after the truth itself has been conjectured. Instead of experiences engendering the inner relations, the inner relations are what engender the experience here.“

Following curiosity

Freud ( 1856–1939 ) considered curiosity and imagination as driving forces of hypothesis building which need to be confronted as quickly as possible with observations. In Beyond the Pleasure Principle , Freud wrote “One may surely give oneself up to a line of thought and follow it up as far as it leads, simply out of scientific curiosity. These innovations were direct translations of observation into theory, subject to no greater sources of error than is inevitable in anything of the kind. At all events there is no way of working out this idea except by combining facts with pure imagination and thereby departing far from observation.” This can quickly go astray when trusting intuition. Freud recommends “that one may inexorably reject theories that are contradicted by the very first steps in the analysis of observation and be aware that those one holds have only a tentative validity.”

Feed‐forward aspects of hypotheses

The geneticist Waddington ( 1905–1975 ) in his essay The Nature of Life states that “a scientific theory cannot remain a mere structure within the world of logic, but must have implications for action and that in two rather different ways. It must involve the consequence that if you do so and so, such and such result will follow. That is to say it must give, or at least offer, the possibility of controlling the process. Secondly, its value is quite largely dependent on its power of suggesting the next step in scientific advance. Any complete piece of scientific work starts with an activity essentially the same as that of an artist. It starts by asking a relevant question. The first step may be a new awareness of some facet of the world that no one else had previously thought worth attending to. Or some new imaginative idea which depends on a sensitive receptiveness to the oddity of nature essentially similar to that of the artist. In his logical analysis and manipulative experimentation, the scientist is behaving arrogantly towards nature, trying to force her into his categories of thought or to trick her into doing what he wants. But finally he has to be humble. He has to take his intuition, his logical theory and his manipulative skill to the bar of Nature and see whether she answers yes or no; and he has to abide by the result. Science is often quite ready to tolerate some logical inadequacy in a theory‐or even a flat logical contradiction like that between the particle and wave theories of matter‐so long as it finds itself in the possession of a hypothesis which offers both the possibility of control and a guide to worthwhile avenues of exploration.”

Poincaré: the dialogue between experiment and hypothesis

Poincaré ( 1854 –1912b) also dealt with physics in Science and Hypothesis . “Experiment is the sole source of truth. It alone can teach us certainty. Cannot we be content with experiment alone? What place is left for mathematical physics? The man of science must work with method. Science is built up of facts, as a house is built of stones, but an accumulation of facts is no more a science than a heap of stones is a house. It is often said that experiments should be made without preconceived concepts. That is impossible. Without the hypothesis, no conclusion could have been drawn; nothing extraordinary would have been seen; and only one fact the more would have been catalogued, without deducing from it the remotest consequence.” Poincaré compares science to a library. Experimental physics alone can enrich the library with new books, but mathematical theoretical physics draw up the catalogue to find the books and to reveal gaps which have to be closed by the purchase of new books.

Poincaré: false, true, fruitful and dangerous hypotheses

Poincaré continues “we all know that there are good and bad experiments. The latter accumulate in vain. Whether there are hundred or thousand, one single piece of work will be sufficient to sweep them into oblivion. Bacon invented the term of an experimentum crucis for such experiments. What then is a good experiment? It is that which teaches us something more than an isolated fact. It is that which enables us to predict and to generalize. Experiments only gives us a certain number of isolated points. They must be connected by a continuous line and that is true generalization. Every generalization is a hypothesis. It should be as soon as possible submitted to verification. If it cannot stand the test, it must be abandoned without any hesitation. The physicist who has just given up one of his hypotheses should rejoice, for he found an unexpected opportunity of discovery. The hypothesis took into account all the known factors which seem capable of intervention in the phenomenon. If it is not verified, it is because there is something unexpected. Has the hypothesis thus rejected been sterile? Far from it. It has rendered more service than a true hypothesis.” Poincaré notes that “with a true hypothesis only one fact the more would have been catalogued, without deducing from it the remotest consequence. It may be said that the wrong hypothesis has rendered more service than a true hypothesis.” However, Poincaré warns that “some hypotheses are dangerous – first and foremost those which are tacit and unconscious. And since we make them without knowing them, we cannot get rid of them.” Poincaré notes that here mathematical physics is of help because by its precision one is compelled to formulate all the hypotheses, revealing also the tacit ones.

Arguments for the reductionist principle

Poincaré also warned against multiplying hypotheses indefinitely: “If we construct a theory upon multiple hypotheses, and if experiment condemns it, which of the premisses must be changed?” Poincaré also recommended to “resolve the complex phenomenon given directly by experiment into a very large number of elementary phenomena. First, with respect to time. Instead of embracing in its entirety the progressive development of a phenomenon, we simply try to connect each moment with the one immediately preceding. Next, we try to decompose the phenomenon in space. We must try to deduce the elementary phenomenon localized in a very small region of space.” Poincaré suggested that the physicist should “be guided by the instinct of simplicity, and that is why in physical science generalization so readily takes the mathematical form to state the problem in the form of an equation.” This argument goes back to Galilei ( 1564 –1642b) who wrote in The Two Sciences “when I observe a stone initially at rest falling from an elevated position and continually acquiring new increments of speed, why should I not believe that such increases take place in a manner which is exceedingly simple and rather obvious to everybody? If now we examine the matter carefully we find no addition or increment more simple than that which repeats itself always in the same manner. It seems we shall not be far wrong if we put the increment of speed as proportional to the increment of time.” With a bit of geometrical reasoning, Galilei deduced that the distance travelled by a freely falling body varies as the square of the time. However, Galilei was not naïve and continued “I grant that these conclusions proved in the abstract will be different when applied in the concrete” and considers disturbances cause by friction and air resistance that complicate the initially conceived simplicity.

Four sequential steps of discovery…

Some philosophers of science attributed a fundamental importance to observations for the acquisition of experience in science. The process starts with accidental observations (Aristotle), going to systematic observations (Bacon), leading to quantitative rules obtained with exact measurements (Newton and Kant) and culminating in observations under artificially created conditions in experiments (Galilei) (Mittelstrass,  1980g ).

…rejected by Popper and Kant

In fact, Newton wrote that he had developed his theory of gravitation from experience followed by induction. K. Popper ( 1902‐1994 ) in his book Conjectures and Refutations did not agree with this logical flow “experience leading to theory” and that for several reasons. This scheme is according to Popper intuitively false because observations are always inexact, while theory makes absolute exact assertions. It is also historically false because Copernicus and Kepler were not led to their theories by experimental observations but by geometry and number theories of Plato and Pythagoras for which they searched verifications in observational data. Kepler, for example, tried to prove the concept of circular planetary movement influenced by Greek theory of the circle being a perfect geometric figure and only when he could not demonstrate this with observational data, he tried elliptical movements. Popper noted that it was Kant who realized that even physical experiments are not prior to theories when quoting Kant's preface to the Critique of Pure Reason : “When Galilei let his globes run down an inclined plane with a gravity which he has chosen himself, then a light dawned on all natural philosophers. They learnt that our reason can only understand what it creates according to its own design; that we must compel Nature to answer our questions, rather than cling to Nature's apron strings and allow her to guide us. For purely accidental observations, made without any plan having been thought out in advance, cannot be connected by a law‐ which is what reason is searching for.” From that reasoning Popper concluded that “we ourselves must confront nature with hypotheses and demand a reply to our questions; and that lacking such hypotheses, we can only make haphazard observations which follow no plan and which can therefore never lead to a natural law. Everyday experience, too, goes far beyond all observations. Everyday experience must interpret observations for without theoretical interpretation, observations remain blind and uninformative. Everyday experience constantly operates with abstract ideas, such as that of cause and effect, and so it cannot be derived from observation.” Popper agreed with Kant who said “Our intellect does not draw its laws from nature…but imposes them on nature”. Popper modifies this statement to “Our intellect does not draw its laws from nature, but tries‐ with varying degrees of success – to impose upon nature laws which it freely invents. Theories are seen to be free creations of our mind, the result of almost poetic intuition. While theories cannot be logically derived from observations, they can, however, clash with observations. This fact makes it possible to infer from observations that a theory is false. The possibility of refuting theories by observations is the basis of all empirical tests. All empirical tests are therefore attempted refutations.”

OUTLOOK: HYPOTHESES IN BIOLOGY

Is biology special.

Waddington notes that “living organisms are much more complicated than the non‐living things. Biology has therefore developed more slowly than sciences such as physics and chemistry and has tended to rely on them for many of its basic ideas. These older physical sciences have provided biology with many firm foundations which have been of the greatest value to it, but throughout most of its history biology has found itself faced with the dilemma as to how far its reliance on physics and chemistry should be pushed” both with respect to its experimental methods and its theoretical foundations. Vitalism is indeed such a theory maintaining that organisms cannot be explained solely by physicochemical laws claiming specific biological forces active in organisms. However, efforts to prove the existence of such vital forces have failed and today most biologists consider vitalism a superseded theory.

Biology as a branch of science is as old as physics. If one takes Aristotle as a reference, he has written more on biology than on physics. Sophisticated animal experiments were already conducted in the antiquity by Galen (Brüssow, 2022 ). Alertus Magnus displayed biological research interest during the medieval time. Knowledge on plants provided the basis of medical drugs in early modern times. What explains biology's decreasing influence compared with the rapid development of physics by Galilei and Newton? One reason is the possibility to use mathematical equations to describe physical phenomena which was not possible for biological phenomena. Physics has from the beginning displayed a trend to few fundamental underlying principles. This is not the case for biology. With the discovery of new continents, biologists were fascinated by the diversity of life. Diversity was the conducting line of biological thinking. This changed only when taxonomists and comparative anatomists revealed recurring pattern in this stunning biological variety and when Darwin provided a theoretical concept to understand variation as a driving force in biology. Even when genetics and molecular biology allowed to understand biology from a few universally shared properties, such as a universal genetic code, biology differed in fundamental aspects from physics and chemistry. First, biology is so far restricted to the planet earth while the laws of physic and chemistry apply in principle to the entire universe. Second, biology is to a great extent a historical discipline; many biological processes cannot be understood from present‐day observations because they are the result of historical developments in evolution. Hence, the importance of Dobzhansky's dictum that nothing makes sense in biology except in the light of evolution. The great diversity of life forms, the complexity of processes occurring in cells and their integration in higher organisms and the importance of a historical past for the understanding of extant organisms, all that has delayed the successful application of mathematical methods in biology or the construction of theoretical frameworks in biology. Theoretical biology by far did not achieve a comparable role as theoretical physics which is on equal foot with experimental physics. Many biologists are even rather sceptical towards a theoretical biology and see progress in the development of ever more sophisticated experimental methods instead in theoretical concepts expressed by new hypotheses.

Knowledge from data without hypothesis?

Philosophers distinguish rational knowledge ( cognitio ex principiis ) from knowledge from data ( cognitio ex data ). Kant associates these two branches with natural sciences and natural history, respectively. The latter with descriptions of natural objects as prominently done with systematic classification of animals and plants or, where it is really history, when describing events in the evolution of life forms on earth. Cognitio ex data thus played a much more prominent role in biology than in physics and explains why the compilation of data and in extremis the collection of museum specimen characterizes biological research. To account for this difference, philosophers of the logical empiricism developed a two‐level concept of science languages consisting of a language of observations (Beobachtungssprache) and a language of theories (Theoriesprache) which are linked by certain rules of correspondence (Korrespondenzregeln) (Carnap,  1891 –1970d). If one looks into leading biological research journals, it becomes clear that biology has a sophisticated language of observation and a much less developed language of theories.

Do we need more philosophical thinking in biology or at least a more vigorous theoretical biology? The breathtaking speed of progress in experimental biology seems to indicate that biology can well develop without much theoretical or philosophical thinking. At the same time, one could argue that some fields in biology might need more theoretical rigour. Microbiologists might think on microbiome research—one of the breakthrough developments of microbiology research in recent years. The field teems with fascinating, but ill‐defined terms (our second genome; holobionts; gut–brain axis; dysbiosis, symbionts; probiotics; health benefits) that call for stricter definitions. One might also argue that biologists should at least consider the criticism of Goethe ( 1749–1832 ), a poet who was also an active scientist. In Faust , the devil ironically teaches biology to a young student.

“Wer will was Lebendigs erkennen und beschreiben, Sucht erst den Geist herauszutreiben, Dann hat er die Teile in seiner Hand, Fehlt, leider! nur das geistige Band.” (To docket living things past any doubt. You cancel first the living spirit out: The parts lie in the hollow of your hand, You only lack the living thing you banned).

We probably need both in biology: more data and more theory and hypotheses.

CONFLICT OF INTEREST

The author reports no conflict of interest.

FUNDING INFORMATION

No funding information provided.

Supporting information

Appendix S1

Brüssow, H. (2022) On the role of hypotheses in science . Microbial Biotechnology , 15 , 2687–2698. Available from: 10.1111/1751-7915.14141 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

• Bacon, F. (1561. –1626) Novum Organum. In: Adler, M.J. (Ed.) (editor‐in‐chief) Great books of the western world . Chicago, IL: Encyclopaedia Britannica, Inc. 2nd edition 1992 vol 1–60 (abbreviated below as GBWW) here: GBWW vol. 28: 128. [ Google Scholar ]
• Brüssow, H. (2022) What is Truth – in science and beyond . Environmental Microbiology , 24 , 2895–2906. [ PubMed ] [ Google Scholar ]
• Carnap, R. (1891. ‐1970a) Philosophical foundations of physics. Ch. 14 . Basic Books, Inc., New York, 1969. [ Google Scholar ]
• Carnap, R. (1891. ‐1970b) Philosophical foundations of physics. Ch. 15 . Basic Books, Inc., New York, 1969. [ Google Scholar ]
• Carnap, R. (1891. ‐1970c) Philosophical foundations of physics. Ch. 16 . Basic Books, Inc., New York, 1969. [ Google Scholar ]
• Carnap, R. (1891. ‐1970d) Philosophical foundations of physics. Ch. 27–28 . Basic Books, Inc., New York, 1969. [ Google Scholar ]
• Copernicus . (1473. ‐1543) Revolutions of heavenly spheres . GBWW , vol. 15 , 505–506. [ Google Scholar ]
• Darwin, C. (1809. ‐1882a) The origin of species . GBWW , vol. 49 : 239. [ Google Scholar ]
• Darwin, C. (1809. ‐1882b) The descent of man . GBWW , vol. 49 : 590. [ Google Scholar ]
• Descartes, R. (1596. ‐1650) Rules for direction . GBWW , vol. 28 , 245. [ Google Scholar ]
• Dewey, J. (1859. –1952) Experience and education . GBWW , vol. 55 , 124. [ Google Scholar ]
• Dorfmüller, T. , Hering, W.T. & Stierstadt, K. (1998) Bergmann Schäfer Lehrbuch der Experimentalphysik: Band 1 Mechanik, Relativität, Wärme. In: Was ist Schwerkraft: Von Newton zu Einstein . Berlin, New York: Walter de Gruyter, pp. 197–203. [ Google Scholar ]
• Einstein, A. (1916) Relativity . GBWW , vol. 56 , 191–243. [ Google Scholar ]
• Einstein, A. & Imfeld, L. (1956) Die Evolution der Physik . Hamburg: Rowohlts deutsche Enzyklopädie, Rowohlt Verlag. [ Google Scholar ]
• Euclid . (c.323‐c.283) The elements . GBWW , vol. 10 , 1–2. [ Google Scholar ]
• Faraday, M. (1791. –1867) Speculation touching electric conduction and the nature of matter . GBWW , 42 , 758–763. [ Google Scholar ]
• Freud, S. (1856. –1939) Beyond the pleasure principle . GBWW , vol. 54 , 661–662. [ Google Scholar ]
• Galilei, G. (1564. ‐1642a) The Assayer, as translated by S. Drake (1957) Discoveries and Opinions of Galileo pp. 237–8 abridged pdf at Stanford University .
• Galilei, G. (1564. ‐1642b) The two sciences . GBWW vol. 26 : 200. [ Google Scholar ]
• Gilbert, W. (1544. ‐1603) On the Loadstone . GBWW , vol. 26 , 108–110. [ Google Scholar ]
• Goethe, J.W. (1749. –1832) Faust . GBWW , vol. 45 , 20. [ Google Scholar ]
• Hilbert, D. (1899) Grundlagen der Geometrie . Leipzig, Germany: Verlag Teubner. [ Google Scholar ]
• Huygens, C. (1617. ‐1670) Treatise on light . GBWW , vol. 32 , 557–560. [ Google Scholar ]
• James, W. (1842. –1907) Principles of psychology . GBWW , vol. 53 , 862–866. [ Google Scholar ]
• Kant, I. (1724. –1804) Critique of pure reason . GBWW , vol. 39 , 227–230. [ Google Scholar ]
• Lavoisier, A.L. (1743. ‐1794) Element of chemistry . GBWW , vol. 42 , p. 2, 6‐7, 9‐10. [ Google Scholar ]
• Locke, J. (1632. ‐1704) Concerning Human Understanding . GBWW , vol. 33 , 317–362. [ Google Scholar ]
• Mittelstrass, J. (1980a) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 1: 239–241 .
• Mittelstrass, J. (1980b) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 3: 307 .
• Mittelstrass, J. (1980c) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 1: 439–442 .
• Mittelstrass, J. (1980d) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 2: 157–158 .
• Mittelstrass, J. (1980e) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 3: 264‐267, 449.450 .
• Mittelstrass, J. (1980f) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 1: 209–210 .
• Mittelstrass, J. (1980g) Enzyklopädie Philosophie und Wissenschaftstheorie Bibliographisches Institut Mannheim, Wien, Zürich B.I. Wissenschaftsverlag Vol. 1: 281–282 .
• Pascal, B. (1623. ‐1662a) Pensées GBWW vol. 30 : 171–173. [ Google Scholar ]
• Pascal, B. (1623. ‐1662b) Scientific treatises on geometric demonstrations . GBWW vol. 30 : 442–443. [ Google Scholar ]
• Plato . (c.424‐c.348 BC a) Timaeus . GBWW , vol. 6 , 442–477. [ Google Scholar ]
• Poincaré, H. (1854. ‐1912a) Science and hypothesis GBWW , vol. 56 : XV‐XVI, 1–5, 10–15 [ Google Scholar ]
• Poincaré, H. (1854. ‐1912b) Science and hypothesis GBWW , vol. 56 : 40–52. [ Google Scholar ]
• Popper, K. (1902. ‐1994) Conjectures and refutations . London and New York, 2002: The Growth of Scientific Knowledge Routledge Classics, pp. 249–261. [ Google Scholar ]
• Syntopicon . (1992) Hypothesis . GBWW , vol. 1 , 576–587. [ Google Scholar ]
• Waddington, C.H. (1905. –1975) The nature of life . GBWW , vol. 56 , 697–699. [ Google Scholar ]

• Cambridge Dictionary +Plus

Definition of hypothesis – Learner’s Dictionary

Your browser doesn't support HTML5 audio

(Definition of hypothesis from the Cambridge Learner's Dictionary © Cambridge University Press)

Translations of hypothesis

Get a quick, free translation!

Word of the Day

compassionate grounds

a reason, especially in law, to allow someone to do something out of sympathy for their suffering

Trial, judge, and jury: talking about what happens when a criminal is caught

Learn more with +Plus

• Recent and Recommended {{#preferredDictionaries}} {{name}} {{/preferredDictionaries}}
• Definitions Clear explanations of natural written and spoken English English Learner’s Dictionary Essential British English Essential American English
• Grammar and thesaurus Usage explanations of natural written and spoken English Grammar Thesaurus
• Pronunciation British and American pronunciations with audio English Pronunciation
• English–Chinese (Simplified) Chinese (Simplified)–English
• English–Chinese (Traditional) Chinese (Traditional)–English
• English–Dutch Dutch–English
• English–French French–English
• English–German German–English
• English–Indonesian Indonesian–English
• English–Italian Italian–English
• English–Japanese Japanese–English
• English–Norwegian Norwegian–English
• English–Polish Polish–English
• English–Portuguese Portuguese–English
• English–Spanish Spanish–English
• English–Swedish Swedish–English
• Dictionary +Plus Word Lists
• Learner’s Dictionary    Noun
• Translations
• All translations

To add hypothesis to a word list please sign up or log in.

Add hypothesis to one of your lists below, or create a new one.

{{message}}

Something went wrong.

There was a problem sending your report.

Comparative Politics Made Simple

Making comparisons.

Most people are subliminal comparativists; others make comparisons their vocation. If you made a decision this morning concerning what to eat, what to wear, and how you should get to work or school, chances are you did so by considering alternatives and choosing the one, for whatever reason, that “made sense” (cereal and milk or eggs and toast? Jeans and t-shirt or suit? Scenic country road or freeway?). You engage in this listing of and picking among alternatives every day, sometimes consciously but often less so. Some decisions you make quickly; for others you insist on taking your time, usually to think through the consequences of each option, before choosing the one that is “best” (that is, the one that is likely to meet your goal with the least possible adverse consequences or costs). To decide is to compare, and most of us decide (and therefore compare) all the time.

Comparative politics is about classifying, comparing, and sometimes even choosing, except that the “things” that are of interest to comparative politics specialists are the really big ones: states, societies, ideologies, political systems, countries, regions, time periods, worlds, and so on. At its most basic, then, comparative politics is a method of study (by comparison) and a field of study (of macrosocial and political phenomena). Comparativists are interested in these phenomena not for their own sake (that’s the job of area studies specialists) but rather for the purpose of drawing attention to similarities and differences — especially the latter, of understanding why things are the way they are in one locale but not another — and of comparing and evaluating realities (for example, public policies).

Looking at Specific Country Examples

A comparativist might observe that the United States’ health-care system is funded mainly by private sources, while the United Kingdom’s system is funded by government (through the National Health Service, or NHS). She further notices that in the U.K. health care is guaranteed to all. But she also notes that those Americans with health insurance have an easier time receiving certain medical procedures (kidney dialysis and transplants, triple-bypass heart surgeries) than their counterparts across the Atlantic. All of the aforementioned differences between the U.S. and U.K. health-care systems are, in and of themselves, interesting, but you probably want to know more, such as why the two countries’ health-care systems are different, and which one is “better.”

Our comparativist is like you, so she investigates. She is not likely to confine herself to health care in the U.S. and the U.K. (her dependent variable): she will focus on other issues that she thinks might have caused health-care systems between the two countries to be so different. These factors (independent variables) would likely include U.S. and U.K. history, geography, demography, economy, political institutions, interest groups, and citizen attitude toward government and the private sector.

She spends hours reading about many possible factors: the insular history of the U.S. and the empire-making history of the U.K. (which favored the formation of a healthy army and civil servants who could be dispatched around the world); the virtual absence of socialist ideology in the mainstream of American politics and the existence of Fabian socialist ideology in the U.K.; the division of policy making between separate, if not to say competing, branches of government in the United States and the fusion of executive and parliamentary powers in the U.K. (which makes for less contention in policy making and implementation); and, above all, her own survey, which indicates that Britons trust government more than Americans do. Our comparativist may now feel that she knows why the health-care systems are different, and may conclude that, although these differences have many causes, one seems to be stronger than all the others: Britons trust government more than Americans. (In some studies comparativists are able to measure, together and separately, the effects of each independent variable, or cause, on the dependent variable, the effect. Even when they cannot do this, they can make plausible arguments about causes and effects.)

What has our comparativist done thus far, and how? First, she observes a “problem” or “case.” Second, she investigates its cause(s). In the process, she reads extensively about not only the health-care systems in the two countries but also their history, political systems, and so forth. The knowledge gained is supplied by secondary sources (for example, the internet, books, or journal articles). To find out about public attitudes toward government and the private sector, the comparativist decides to do a survey. Information supplied by this survey may be said to have come from primary sources . The comparativist therefore uses two types of sources to gather facts, which she analyzes meticulously to make a case as to why health-care systems in the U.S. and the U.K. are different. But she may go even further than that, based on what she has learned from her study. She may conclude that, given the evidence, one country has a “better” health-care system than the other. Here, however, she would be expressing a preference: her research would thus have a normative (or value-based) dimension, not just a positive (value-neutral or empirical) one. Furthermore, she may develop a theory , which is a general statement intended to explain or account for a given phenomenon, about health-care systems: citizen trust in government is the reason why countries have government-funded health-care systems.

National and Global Contexts

The terms in bold are at the heart of comparative politics. The U.S. and the U.K. are countries, or, in comparative politics language, nation-states . A nation-state is a large group of people who share (a) the characteristics of history, language, religion, ethnicity, race, political and economic values, and so forth; (b) occupy the same (usually contiguous) territory; and (c) have a government that they recognize as “theirs,” which makes laws and regulations and is expected to defend them in case of an attack by another government. Few countries neatly fit this definition. The U.S., for example, has many ethnic groups and religions. Perhaps a better concept than nation-state is a national state, in which a large group of people living under one authority (or state) have come together to forge a common or national identity, regardless of other things that may separate them. Nation-states are usually the units of analysis in comparative research, but comparativists can focus on almost anything. A unit of analysis is the main object or actor in an argument, hypothesis, or theoretical framework. It is different from the levels of analysis , which are the primary analytical focus of the researcher, which in our example would be American and British health-care systems or policies.

Nevertheless, comparativists almost never ignore certain macrosocial factors, even when they are not their primary focus of study. These would include the economy , which is whatever arrangement people make to produce and trade the goods and services that they think they need to survive, or otherwise make money; the state , which is the centralized authority that rules over a territory thanks to its monopolistic ownership of force (armies, police, militias, etc.); and political institutions , or the means by which state power is organized. Macrosocial factors also include ideology , or the worldview by which people make sense of reality and, at the same time, serves as a guide for them to do what is “right”; culture , which is the purported collective experience, characteristics, and orientation of a large group of people (closely related to ideology, but not the same: ideology is a cognitive road map usually produced by elites [intellectuals no less], and culture is how people actually live); civil society , which refers to nonstate organizations that people voluntarily join, usually to defend their interests against the state or express themselves peacefully and nonpolitically (political parties, labor unions, Girl Scouts, etc.); and, finally, the international environment , which refers to actors external to the typical units of analysis (nation-states) of comparativists.

The international environment is composed of other nation-states or countries, multinational, government-sanctioned institutions , which are institutions created by many nation-states to address matters of common concern (for example, the United Nations); multinational, privately owned corporations , which are profit-seeking business organizations that operate in more than one country (for example Wal-Mart); and international nongovernmental organizations (INGOs), which are non-profit-seeking organizations that operate on a charity basis and deliver services to the poor and needy across countries (such as Doctors Without Borders). INGOS also serve as advocates when they do not provide services (for example, Amnesty International).

You can pick almost any book on comparative politics and you will find at least a mention of the concepts defined above. Sometimes one is the focus of comparison in a two-country study, as when comparativists study political parties in the U.S. and Italy. Sometimes they are bundled with others in a multicountry study, as when comparativists study democracy and economic development all over the world. The relative weight of specific concepts as explanatory variables in the analysis of comparativists largely determines the “school” to which they may be said to belong.

Schools of Analysis

Three of the most prominent schools in comparative politics in the past 50 years have been political economy , modernization theory , and dependency theory . They are chosen here only to give you an idea of the sharply different perspectives that exist in comparative politics. The political economy approach emphasizes, as its name suggests, the nexus between economy and politics. A classic case is Robert Bates’s States and Markets in Tropical Africa: The Political Basis of Agricultural Policy (University of California Press, 1981), in which the author examines how state economic policy in Africa, especially in agriculture, undermines development, and why policy continues in light of failure. Political economy, in turn, is composed of subschools, among them rational choice theory, which attempts to use (neoclassical) economic reasoning to explain collective decisions.

Like political economy, modernization theory focuses on domestic forces, but its concern is more about how certain cultural aspects that retard development may be overcome. Modernization theory generally divides society between a “modern” sector and a “backward” sector. The challenge of development is how to overcome the latter. In addition, modernization theory tends to emphasize culture rather than the political economy, which it sees as a dependent variable to be acted upon. Still, the units of analysis in both schools are nation-states, and their levels of analysis, although different, are internal to the units. 1

The same cannot be said of dependency theory, for which the global system, not nation-states, is the focus of analysis. In dependency theory, poverty is due to neither so-called backward culture nor deleterious state actions in the political economy but rather the global system itself: a relatively small number of “core” countries specialize in high-value-added manufactured goods, while a large number of “peripheral” countries specialize in primary commodity production. Thus poverty in dependency theory stems from the position countries occupy in the international division of labor or system.

To conclude, comparative politics is about serious issues: war and peace, democracy and authoritarianism, market-based and state-based economies, prosperity and poverty, health-care coverage, and so on. However, its raison d’être is quite simple: the world is diverse, not monolithic. Furthermore, the world is getting smaller, literally and figuratively. Given the tremendous diversity that exists on our planet, and the fact that no one country is “better” than all the others on every count, there is always room for learning. Furthermore, knowledge is a precondition for success in an interdependent – less isolated, more interconnected, and therefore “smaller” – world. How can we relate to another country if we know nothing about its institutions, culture, or history? The job of the comparativist researcher is to make comparisons less subliminal and random, and more deliberate and systematic, especially in the things that are critical to human life.

1. I am simplifying somewhat here. Allowance should be made for international political economy, which emphasizes the role of external forces in the politics of countries. Also, modernization theory stresses the demonstration effect that “modern” countries have on their nonmodern cousins.

Authored by

Jean-Germain Gros University of Missouri-St. Louis St. Louis, Missouri,

: an idea or theory that is not proven but that leads to further study or discussion

Full Definition of HYPOTHESIS

Examples of hypothesis.

• In contrast to Bingham's hypothesis that Machu Picchu was the birthplace of the first Inca and the hearth area of the Inca civilization, current scholars believe that the city was built as a country estate … —Roger Balm, Focus On Geography , Spring 2004
• Campus veterans marvel at all the poolside apartments that have sprung up since Georgia popped the income cap off its merit awards. Professors are testing their hypothesis that instead of increasing college enrollment, the state's $1.7 billion scholarship program has been a blessing for the automobile industry—since so many families roll the savings into buying new cars. —Greg Winter, New York Times , 31 Oct. 2002
• Isaac Newton initially argued against a parabolic orbit for the … comet of 1680, preferring the hypothesis of two independent comets, one for the inbound and one for the outbound leg. However, Newton later showed that the orbit of the comet could indeed be fit by a parabola. — “ Physics and Chemistry of Comets, ” Daniel C. Boice and Walter Huebner in Encyclopedia of the Solar System Paul R. Weissman et al., editors , 1999
• As stated, our working hypothesis suggests a straightforward way to look for evidence that would confirm or disconfirm it: can you predict what is omitted and what is included in alphabetic representations? —Timothy Shopen and Joseph M. Williams, Standards and Dialects in English , 1980
• [+] more [-] hide

Origin of HYPOTHESIS

Related to hypothesis, synonym discussion of hypothesis, definition of hypothesis for kids, medical definition of hypothesis, learn more about hypothesis.

• accretionary hypothesis
• autotroph hypothesis
• granular hypothesis
• heterotroph hypothesis
• nebular hypothesis
• null hypothesis
• planetesimal hypothesis
• Prout's hypothesis
• Sapir-Whorf hypothesis
• tetrahedral hypothesis
• Thomson's hypothesis
• unitarian hypothesis
• Wegener hypothesis
• Whorfian hypothesis
• working hypothesis
• age and area concept
• Alvarez theory
• micellar theory

Seen & Heard

What made you want to look up hypothesis ? Please tell us where you read or heard it (including the quote, if possible).

• Spanish Central
• Learner's ESL Dictionary
• WordCentral for Kids
• Visual Dictionary
• SCRABBLE ® Word Finder
• Merriam-Webster's Unabridged Dictionary
• Britannica English - Arabic Translation
• Nglish - Spanish-English Translation
• Advertising Info
• Dictionary API
• Privacy Policy
• Terms of Use
• About Our Ads
• Browser Tools
• The Open Dictionary
• Browse the Dictionary
• Browse the Thesaurus
• Browse the Spanish-English Dictionary
• Browse the Medical Dictionary

Official websites use .gov

A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Births in the United States, 2023

NCHS Data Brief No. 507, August 2024

PDF Version (454 KB)

Joyce A. Martin, M.P.H., Brady E. Hamilton Ph.D., and Michelle J.K. Osterman, M.H.S.

• Key findings

The number of births and the general fertility rate declined from 2022 to 2023.

Birth rates declined for females ages 15–19 from 2022 to 2023., prenatal care beginning in the first trimester declined for the second year in a row in 2023., the preterm birth rate was unchanged from 2022 to 2023, but early-term births increased., data source and methods, about the authors, suggested citation.

Data from the National Vital Statistics System

• The number of births in the United States declined 2% from 2022 to 2023. The general fertility rate declined 3% in 2023 to 54.5 births per 1,000 females ages 15–44.
• Birth rates declined for females ages 15–19 (4%), 15–17 (2%), and 18–19 (5%), from 2022 to 2023.
• The percentage of mothers receiving prenatal care in the first trimester of pregnancy declined 1% from 2022 to 2023, while the percentage of mothers with no prenatal care increased 5%.
• The preterm birth rate was essentially unchanged at 10.41% in 2023, but the rate of early-term births rose 2% to 29.84%.

This report presents highlights from 2023 final birth data on key demographic and maternal and infant health indicators. The number of births, the general fertility rate (births per 1,000 females ages 15–44), teen birth rates, the distribution of births by trimester prenatal care began, and the distribution of births by gestational age (less than 37 weeks, 37–38 weeks, 39–40 weeks, and 41 or later weeks of gestation) are presented. For all indicators, results for 2023 are compared with those for 2022 and 2021.

Keywords : general fertility rate, prenatal care, gestational age, National Vital Statistics System.

• In 2023, 3,596,017 births were registered in the United States, down 2% from 2022 (3,667,758) and 2021 (3,664,292) ( Figure 1 , Table 1 ).
• The general fertility rate for the United States decreased 3% in 2023 to 54.5 births per 1,000 females ages 15–44 from 56.0 in 2022; the general fertility rate was also down 3% from 2021 (56.3).

Figure 1. Number of live births and general fertility rates: United States, 2021–2023

NOTES: General fertility rates are births per 1,000 women ages 15–44. Rates are based on population estimates as of July 1 for 2021, 2022, and 2023. SOURCE: National Center for Health Statistics, National Vital Statistics System, natality data file.

• The birth rate for teenagers ages 15–19 declined 4% from 2022 to 2023, from 13.6 to 13.1 births per 1,000 females, and was down 6% from 2021 (13.9) ( Figure 2 , Table 2 ).
• From 2022 to 2023, the birth rate for teenagers ages 15–17 declined 2%, from 5.6 to 5.5; there was no change in the rate from 2021 to 2022.
• The rate for teenagers ages 18–19 declined 5% from 2022 to 2023, from 25.8 to 24.6 and has declined 8% since 2021 (26.6).

Figure 2. Birth rate for teenagers, by maternal age: United States, 2021–2023

NOTES: Age-specific birth rates are births per 1,000 females in specified age group. Rates are based on population estimates as of July 1 for each year 2021–2023. SOURCE: National Center for Health Statistics, National Vital Statistics System, natality data file.

• Prenatal care beginning in the first trimester declined 1% in 2023 to 76.1%, from 77.0% in 2022. This follows a 2% decline from 2021 (78.3%) to 2022 ( Figure 3 , Table 3 ).
• Care beginning in the second trimester increased 4% in 2023, from 16.3% in 2022 to 16.9%. This follows a 6% increase from 2021 (15.4%).
• Care beginning in the third trimester increased 2% from 2022 (4.6%) to 2023 (4.7%) following a 10% increase from 2021 (4.2%) to 2022.
• The percentage of mothers receiving no prenatal care increased 5% in 2023 to 2.3% from 2.2% in 2022; the percentage of mothers with no prenatal care also rose 5% from 2021 (2.1%) to 2022.

Figure 3. Distribution of trimester prenatal care began: United States, 2021–2023

SOURCE: National Center for Health Statistics, National Vital Statistics System, natality data file.

• The percentage of infants born preterm was essentially unchanged from 2022 (10.38%) to 2023 (10.41%) but was down 1% from 2021 (10.49%) ( Figure 4 , Table 4 ).
• The percentage of infants born early term rose 2% from 2022 to 2023, from 29.31% to 29.84%, and was up 4% from 2021 (28.76%).
• In contrast, the percentage of full-term births declined 1%, from 2022 to 2023 (55.32% to 54.94%) and has declined 2% since 2021 (55.90%).
• The percentage of infants born late or post term was 4.82% in 2023, down 3% from 2022 (4.99%) and 1% from 2021 (4.85%).

Figure 4. Distribution of births by gestational age: United States, 2021–2023

NOTES: Preterm is less than 37 weeks, early term is 37 to 38 weeks, full term is 39 to 40 weeks, and late and post-term is 41 weeks or more. Source: National Center for Health Statistics, National Vital Statistics System, natality data file. SOURCE: National Center for Health Statistics, National Vital Statistics System, natality data file.

U.S. birth certificate data for 2023 show continued declines in the number (2%) and rate (3%) of births from 2022 to 2023. Since the most recent high in 2007, the number of births has declined 17%, and the general fertility rate has declined 21% ( 1 ). The teen birth rate also continued to decline in 2023 and has declined two-thirds since 2007 ( 1 ). The percentage of women beginning care in the first trimester of pregnancy declined in 2023 and was down 3% from the most recent high in 2021; first trimester care had been on the rise from 2016 to 2021. At the same time, the percentage of women with late care or with no care rose from 2021 to 2023; late and no-care levels have risen steadily since 2016 ( 1 ). The preterm birth rate was essentially unchanged from 2022 to 2023, but early-term births rose 2%, and full-term and late- and post-term births declined 1% and 3%, respectively. Since the most recent low in 2014, preterm birth rates have risen 9% and early-term births by 21%, while full-term and late- and post-term births have declined ( 1 ).

General fertility rate : Number of births per 1,000 females ages 15–44.

Gestational age : Preterm is births delivered before 37 completed weeks of gestation, early term is 37–38 weeks, full term is 39–40 weeks, and late and post term is 41 or later weeks. Gestational age is based on the obstetric estimate of gestation in completed weeks.

Teenage birth rates : Births per 1,000 females in the specified age groups 15–19, 15–17, and 18–19.

Trimester prenatal care began : The timing of care based on the date a physician or other health care provider examined or counseled the pregnant woman for the pregnancy and the obstetric estimate of gestational age.

This report uses data from the natality data file from the National Vital Statistics System. The vital statistics natality file is based on information from birth certificates and includes information for all births occurring in the United States. This Data Brief accompanies the release of the 2023 natality public-use file ( 2 ). More detailed analyses of the topics presented in this report and other topics such as births by age of mother, tobacco use during pregnancy, pregnancy risk factors, prenatal care timing and utilization, receipt of WIC food, maternal body mass index, and breastfeeding are possible by using the annual natality files ( 2 ). Additional information from the 2023 final birth data file is available via the CDC WONDER platform and will be included in the final 2023 National Vital Statistics Births Report.

References to increases or decreases in rates or percentages indicate differences are statistically significant at the 0.05 level based on a two-tailed z test. References to decreases in the number of births indicate differences are statistically significant at the 0.05 level based on a two-tailed chi-squared test. Computations exclude records for which information is unknown.

Rates shown in this report are based on population estimates calculated from a base that incorporates the 2020 census, vintage 2020 estimates for April 1, 2020, and 2020 demographic analysis estimates. Rates are calculated based on population estimates as of July 1, 2022, (vintage 2022) and July 1, 2023 (vintage 2023) ( 1 , 3 ). The vintage 2023 population estimates include methodological changes made after the release of the vintage 2022 population estimates and projection ( 4 , 5 ). Changes in rates from 2022 to 2023 reflect changes in births and changes in population estimates.

Joyce A. Martin, Brady E. Hamilton, and Michelle J.K. Osterman are with the National Center for Health Statistics, Division of Vital Statistics.

• Osterman MJK, Hamilton BE, Martin JA, Driscoll AK, Valenzuela CP. Births: Final data for 2022. National Vital Statistics Reports; vol 73 no 1. Hyattsville, MD: National Center for Health Statistics. 2024. DOI: https://dx.doi.org/10.15620/cdc:145588
• National Center for Health Statistics. Vital statistics online data portal .
• U.S. Census Bureau. Annual state resident population estimates for six race groups (five race alone groups and two or more races) by age, sex, and Hispanic origin: April 1, 2010, to July 1, 2023 . 2024.
• U.S. Census Bureau. Methodology for the United States population estimates: Vintage 2023 . Nation, states, counties, and Puerto Rico—April 1, 2010 to July 1, 2023. 2023.
• U.S. Census Bureau. Vintage 2023 release notes . 2024.

Martin JA, Hamilton BE, Osterman MJK. Births in the United States, 2023. NCHS Data Brief, no 507. Hyattsville, MD: National Center for Health Statistics. 2024. DOI: https://dx.doi.org/10.15620/cdc/158789 .

Copyright information

All material appearing in this report is in the public domain and may be reproduced or copied without permission; citation as to source, however, is appreciated.

National Center for Health Statistics

Brian C. Moyer, Ph.D., Acting Director Amy M. Branum, Ph.D., Associate Director for Science

Division of Vital Statistics

Paul D. Sutton, Ph.D., Acting Director Andrés A. Berruti, Ph.D., M.A., Associate Director for Science

• Get E-mail Updates
• Data Visualization Gallery
• NHIS Early Release Program
• MMWR QuickStats
• Government Printing Office Bookstore