scientific hypothesis and theory

This is the Difference Between a Hypothesis and a Theory

What to Know A hypothesis is an assumption made before any research has been done. It is formed so that it can be tested to see if it might be true. A theory is a principle formed to explain the things already shown in data. Because of the rigors of experiment and control, it is much more likely that a theory will be true than a hypothesis.

As anyone who has worked in a laboratory or out in the field can tell you, science is about process: that of observing, making inferences about those observations, and then performing tests to see if the truth value of those inferences holds up. The scientific method is designed to be a rigorous procedure for acquiring knowledge about the world around us.

In scientific reasoning, a hypothesis is constructed before any applicable research has been done. A theory, on the other hand, is supported by evidence: it's a principle formed as an attempt to explain things that have already been substantiated by data.

Toward that end, science employs a particular vocabulary for describing how ideas are proposed, tested, and supported or disproven. And that's where we see the difference between a hypothesis and a theory .

A hypothesis is an assumption, something 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.

What is a Hypothesis?

A hypothesis is usually tentative, an assumption or suggestion made strictly for the objective of being tested.

When a character which has been lost in a breed, reappears after a great number of generations, the most probable hypothesis is, not that the offspring suddenly takes after an ancestor some hundred generations distant, but that in each successive generation there has been a tendency to reproduce the character in question, which at last, under unknown favourable conditions, gains an ascendancy. Charles Darwin, On the Origin of Species , 1859 According to one widely reported hypothesis , cell-phone transmissions were disrupting the bees' navigational abilities. (Few experts took the cell-phone conjecture seriously; as one scientist said to me, "If that were the case, Dave Hackenberg's hives would have been dead a long time ago.") Elizabeth Kolbert, The New Yorker , 6 Aug. 2007

What is a Theory?

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, its likelihood as truth is much higher than that of a hypothesis.

It is evident, on our theory , that coasts merely fringed by reefs cannot have subsided to any perceptible amount; and therefore they must, since the growth of their corals, either have remained stationary or have been upheaved. Now, it is remarkable how generally it can be shown, by the presence of upraised organic remains, that the fringed islands have been elevated: and so far, this is indirect evidence in favour of our theory . Charles Darwin, The Voyage of the Beagle , 1839 An example of a fundamental principle in physics, first proposed by Galileo in 1632 and extended by Einstein in 1905, is the following: All observers traveling at constant velocity relative to one another, should witness identical laws of nature. From this principle, Einstein derived his theory of special relativity. Alan Lightman, Harper's , December 2011

Non-Scientific Use

In non-scientific use, however, hypothesis and theory are often used interchangeably to mean simply an idea, speculation, or hunch (though theory is more common in this regard):

The theory of the teacher with all these immigrant kids was that if you spoke English loudly enough they would eventually understand. E. L. Doctorow, Loon Lake , 1979 Chicago is famous for asking questions for which there can be no boilerplate answers. Example: given the probability that the federal tax code, nondairy creamer, Dennis Rodman and the art of mime all came from outer space, name something else that has extraterrestrial origins and defend your hypothesis . John McCormick, Newsweek , 5 Apr. 1999 In his mind's eye, Miller saw his case suddenly taking form: Richard Bailey had Helen Brach killed because she was threatening to sue him over the horses she had purchased. It was, he realized, only a theory , but it was one he felt certain he could, in time, prove. Full of urgency, a man with a mission now that he had a hypothesis to guide him, he issued new orders to his troops: Find out everything you can about Richard Bailey and his crowd. Howard Blum, Vanity Fair , January 1995

And sometimes one term is used as a genus, or a means for defining the other:

Laplace's popular version of his astronomy, the Système du monde , was famous for introducing what came to be known as the nebular hypothesis , the theory that the solar system was formed by the condensation, through gradual cooling, of the gaseous atmosphere (the nebulae) surrounding the sun. Louis Menand, The Metaphysical Club , 2001 Researchers use this information to support the gateway drug theory — the hypothesis that using one intoxicating substance leads to future use of another. Jordy Byrd, The Pacific Northwest Inlander , 6 May 2015 Fox, the business and economics columnist for Time magazine, tells the story of the professors who enabled those abuses under the banner of the financial theory known as the efficient market hypothesis . Paul Krugman, The New York Times Book Review , 9 Aug. 2009

Incorrect Interpretations of "Theory"

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 use 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."

More Differences Explained

• Epidemic vs. Pandemic
• Diagnosis vs. Prognosis
• Treatment vs. Cure

Word of the Day

See Definitions and Examples »

Get Word of the Day daily email!

Games & Quizzes

Commonly Confused

'canceled' or 'cancelled', 'virus' vs. 'bacteria', your vs. you're: how to use them correctly, is it 'jail' or 'prison', 'deduction' vs. 'induction' vs. 'abduction', grammar & usage, every letter is silent, sometimes: a-z list of examples, how to use em dashes (—), en dashes (–) , and hyphens (-), the difference between 'i.e.' and 'e.g.', plural and possessive names: a guide, 31 useful rhetorical devices, pilfer: how to play and win, 8 words with fascinating histories, flower etymologies for your spring garden, 8 words for lesser-known musical instruments, it's a scorcher words for the summer heat.

Hypothesis vs. Theory

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science , a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

Comparison chart

Examples of Theory and Hypothesis

Theory: Einstein's theory of relativity is a theory because it has been tested and verified innumerable times, with results consistently verifying Einstein's conclusion. However, simply because Einstein's conclusion has become a theory does not mean testing of this theory has stopped; all science is ongoing. See also the Big Bang theory , germ theory , and climate change .

Hypothesis: One might think that a prisoner who learns a work skill while in prison will be less likely to commit a crime when released. This is a hypothesis, an "educated guess." The scientific method can be used to test this hypothesis, to either prove it is false or prove that it warrants further study. (Note: Simply because a hypothesis is not found to be false does not mean it is true all or even most of the time. If it is consistently true after considerable time and research, it may be on its way to becoming a theory.)

This video further explains the difference between a theory and a hypothesis:

Common Misconception

People often tend to say "theory" when what they're actually talking about is a hypothesis. For instance, "Migraines are caused by drinking coffee after 2 p.m. — well, it's just a theory, not a rule."

This is actually a logically reasoned proposal based on an observation — say 2 instances of drinking coffee after 2 p.m. caused a migraine — but even if this were true, the migraine could have actually been caused by some other factors.

Because this observation is merely a reasoned possibility, it is testable and can be falsified — which makes it a hypothesis, not a theory.

• What is a Scientific Hypothesis? - LiveScience
• Wikipedia:Scientific theory

Related Comparisons

Share this comparison via:

If you read this far, you should follow us:

"Hypothesis vs Theory." Diffen.com. Diffen LLC, n.d. Web. 17 Aug 2024. < >

Comments: Hypothesis vs Theory

Anonymous comments (2).

October 11, 2013, 1:11pm "In science, a theory is a well-substantiated, unifying explanation for a set of verified, proven hypotheses." But there's no such thing as "proven hypotheses". Hypotheses can be tested/falsified, they can't be "proven". That's just not how science works. Logical deductions based on axioms can be proven, but not scientific hypotheses. On top of that I find it somewhat strange to claim that a theory doesn't have to be testable, if it's built up from hypotheses, which DO have to be testable... — 80.✗.✗.139

May 6, 2014, 11:45pm "Evolution is a theory, not a fact, regarding the origin of living things." this statement is poorly formed because it implies that a thing is a theory until it gets proven and then it is somehow promoted to fact. this is just a misunderstanding of what the words mean, and of how science progresses generally. to say that a theory is inherently dubious because "it isn't a fact" is pretty much a meaningless statement. no expression which qualified as a mere fact could do a very good job of explaining the complicated process by which species have arisen on Earth over the last billion years. in fact, if you claimed that you could come up with such a single fact, now THAT would be dubious! everything we observe in nature supports the theory of evolution, and nothing we observe contradicts it. when you can say this about a theory, it's a pretty fair bet that the theory is correct. — 71.✗.✗.151

• Accuracy vs Precision
• Deductive vs Inductive
• Subjective vs Objective
• Subconscious vs Unconscious mind
• Qualitative vs Quantitative
• Creationism vs Evolution

Edit or create new comparisons in your area of expertise.

Stay connected

© All rights reserved.

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• Science Experiments for Kids
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

Scientific Theory Definition and Examples

A scientific theory is a well-established explanation of some aspect of the natural world. Theories come from scientific data and multiple experiments. While it is not possible to prove a theory, a single contrary result using the scientific method can disprove it. In other words, a theory is testable and falsifiable.

Examples of Scientific Theories

There are many scientific theory in different disciplines:

• Astronomy : theory of stellar nucleosynthesis , theory of stellar evolution
• Biology : cell theory, theory of evolution, germ theory, dual inheritance theory
• Chemistry : atomic theory, Bronsted Lowry acid-base theory , kinetic molecular theory of gases , Lewis acid-base theory , molecular theory, valence bond theory
• Geology : climate change theory, plate tectonics theory
• Physics : Big Bang theory, perturbation theory, theory of relativity, quantum field theory

Criteria for a Theory

In order for an explanation of the natural world to be a theory, it meets certain criteria:

• A theory is falsifiable. At some point, a theory withstands testing and experimentation using the scientific method.
• A theory is supported by lots of independent evidence.
• A theory explains existing experimental results and predicts outcomes of new experiments at least as well as other theories.

Difference Between a Scientific Theory and Theory

Usually, a scientific theory is just called a theory. However, a theory in science means something different from the way most people use the word. For example, if frogs rain down from the sky, a person might observe the frogs and say, “I have a theory about why that happened.” While that theory might be an explanation, it is not based on multiple observations and experiments. It might not be testable and falsifiable. It’s not a scientific theory (although it could eventually become one).

Value of Disproven Theories

Even though some theories are incorrect, they often retain value.

For example, Arrhenius acid-base theory does not explain the behavior of chemicals lacking hydrogen that behave as acids. The Bronsted Lowry and Lewis theories do a better job of explaining this behavior. Yet, the Arrhenius theory predicts the behavior of most acids and is easier for people to understand.

Another example is the theory of Newtonian mechanics. The theory of relativity is much more inclusive than Newtonian mechanics, which breaks down in certain frames of reference or at speeds close to the speed of light . But, Newtonian mechanics is much simpler to understand and its equations apply to everyday behavior.

Difference Between a Scientific Theory and a Scientific Law

The scientific method leads to the formulation of both scientific theories and laws . Both theories and laws are falsifiable. Both theories and laws help with making predictions about the natural world. However, there is a key difference.

A theory explains why or how something works, while a law describes what happens without explaining it. Often, you see laws written in the form of equations or formulas.

Theories and laws are related, but theories never become laws or vice versa.

Theory vs Hypothesis

A hypothesis is a proposition that is tested via an experiment. A theory results from many, many tested hypotheses.

Theory vs Fact

Theories depend on facts, but the two words mean different things. A fact is an irrefutable piece of evidence or data. Facts never change. A theory, on the other hand, may be modified or disproven.

Difference Between a Theory and a Model

Both theories and models allow a scientist to form a hypothesis and make predictions about future outcomes. However, a theory both describes and explains, while a model only describes. For example, a model of the solar system shows the arrangement of planets and asteroids in a plane around the Sun, but it does not explain how or why they got into their positions.

• Frigg, Roman (2006). “ Scientific Representation and the Semantic View of Theories .”  Theoria . 55 (2): 183–206. 
• Halvorson, Hans (2012). “What Scientific Theories Could Not Be.”  Philosophy of Science . 79 (2): 183–206. doi: 10.1086/664745
• McComas, William F. (December 30, 2013).  The Language of Science Education: An Expanded Glossary of Key Terms and Concepts in Science Teaching and Learning . Springer Science & Business Media. ISBN 978-94-6209-497-0.
• National Academy of Sciences (US) (1999). Science and Creationism: A View from the National Academy of Sciences (2nd ed.). National Academies Press. doi: 10.17226/6024  ISBN 978-0-309-06406-4. 
• Suppe, Frederick (1998). “Understanding Scientific Theories: An Assessment of Developments, 1969–1998.”  Philosophy of Science . 67: S102–S115. doi: 10.1086/392812

Related Posts

Hypothesis, Model, Theory, and Law

Dorling Kindersley / Getty Images

• Physics Laws, Concepts, and Principles
• Quantum Physics
• Important Physicists
• Thermodynamics
• Cosmology & Astrophysics
• Weather & Climate

• M.S., Mathematics Education, Indiana University
• B.A., Physics, Wabash College

In common usage, the words hypothesis, model, theory, and law have different interpretations and are at times used without precision, but in science they have very exact meanings.

Perhaps the most difficult and intriguing step is the development of a specific, testable hypothesis. A useful hypothesis enables predictions by applying deductive reasoning, often in the form of mathematical analysis. It is a limited statement regarding the cause and effect in a specific situation, which can be tested by experimentation and observation or by statistical analysis of the probabilities from the data obtained. The outcome of the test hypothesis should be currently unknown, so that the results can provide useful data regarding the validity of the hypothesis.

Sometimes a hypothesis is developed that must wait for new knowledge or technology to be testable. The concept of atoms was proposed by the ancient Greeks , who had no means of testing it. Centuries later, when more knowledge became available, the hypothesis gained support and was eventually accepted by the scientific community, though it has had to be amended many times over the year. Atoms are not indivisible, as the Greeks supposed.

A model is used for situations when it is known that the hypothesis has a limitation on its validity. The Bohr model of the atom , for example, depicts electrons circling the atomic nucleus in a fashion similar to planets in the solar system. This model is useful in determining the energies of the quantum states of the electron in the simple hydrogen atom, but it is by no means represents the true nature of the atom. Scientists (and science students) often use such idealized models  to get an initial grasp on analyzing complex situations.

Theory and Law

A scientific theory or law represents a hypothesis (or group of related hypotheses) which has been confirmed through repeated testing, almost always conducted over a span of many years. Generally, a theory is an explanation for a set of related phenomena, like the theory of evolution or the big bang theory . 

The word "law" is often invoked in reference to a specific mathematical equation that relates the different elements within a theory. Pascal's Law refers an equation that describes differences in pressure based on height. In the overall theory of universal gravitation developed by Sir Isaac Newton , the key equation that describes the gravitational attraction between two objects is called the law of gravity .

These days, physicists rarely apply the word "law" to their ideas. In part, this is because so many of the previous "laws of nature" were found to be not so much laws as guidelines, that work well within certain parameters but not within others.

Scientific Paradigms

Once a scientific theory is established, it is very hard to get the scientific community to discard it. In physics, the concept of ether as a medium for light wave transmission ran into serious opposition in the late 1800s, but it was not disregarded until the early 1900s, when Albert Einstein proposed alternate explanations for the wave nature of light that did not rely upon a medium for transmission.

The science philosopher Thomas Kuhn developed the term scientific paradigm to explain the working set of theories under which science operates. He did extensive work on the scientific revolutions that take place when one paradigm is overturned in favor of a new set of theories. His work suggests that the very nature of science changes when these paradigms are significantly different. The nature of physics prior to relativity and quantum mechanics is fundamentally different from that after their discovery, just as biology prior to Darwin’s Theory of Evolution is fundamentally different from the biology that followed it. The very nature of the inquiry changes.

One consequence of the scientific method is to try to maintain consistency in the inquiry when these revolutions occur and to avoid attempts to overthrow existing paradigms on ideological grounds.

Occam’s Razor

One principle of note in regards to the scientific method is Occam’s Razor (alternately spelled Ockham's Razor), which is named after the 14th century English logician and Franciscan friar William of Ockham. Occam did not create the concept—the work of Thomas Aquinas and even Aristotle referred to some form of it. The name was first attributed to him (to our knowledge) in the 1800s, indicating that he must have espoused the philosophy enough that his name became associated with it.

The Razor is often stated in Latin as:

entia non sunt multiplicanda praeter necessitatem

or, translated to English:

entities should not be multiplied beyond necessity

Occam's Razor indicates that the most simple explanation that fits the available data is the one which is preferable. Assuming that two hypotheses presented have equal predictive power, the one which makes the fewest assumptions and hypothetical entities takes precedence. This appeal to simplicity has been adopted by most of science, and is invoked in this popular quote by Albert Einstein:

Everything should be made as simple as possible, but not simpler.

It is significant to note that Occam's Razor does not prove that the simpler hypothesis is, indeed, the true explanation of how nature behaves. Scientific principles should be as simple as possible, but that's no proof that nature itself is simple.

However, it is generally the case that when a more complex system is at work there is some element of the evidence which doesn't fit the simpler hypothesis, so Occam's Razor is rarely wrong as it deals only with hypotheses of purely equal predictive power. The predictive power is more important than the simplicity.

Edited by Anne Marie Helmenstine, Ph.D.

• The Basics of Physics in Scientific Study
• Kinetic Molecular Theory of Gases
• De Broglie Hypothesis
• An Introduction to Brownian Motion
• The History of Gravity
• History of the Michelson-Morley Experiment
• Newton's Law of Gravity
• Wave Particle Duality and How It Works
• What Is the Boltzmann Brains Hypothesis?
• Five Great Problems in Theoretical Physics
• The Basics of String Theory
• Understanding Cosmology and Its Impact
• Albert Einstein: What Is Unified Field Theory?
• What Is the Steady-State Theory in Cosmology?
• An Idealized Model in Physics
• What Is Model-Dependent Realism?

“Theory” vs. “Hypothesis”: What Is The Difference?

Chances are you’ve heard of the TV show The Big Bang Theory . Lots of people love this lighthearted sitcom for its quirky characters and their relationships, but others haven’t even given the series a chance for one reason: they don’t like science and assume the show is boring.

However, it only takes a few seconds with Sheldon and Penny to disprove this assumption and realize that this theory ab0ut The Big Bang Theory is wrong—it isn’t a scientific snoozefest.

But wait: is it a theory or a  hypothesis about the show that leads people astray? And would the actual big bang theory— the one that refers to the beginning of the universe—mean the same thing as a big bang hypothesis ?

Let’s take a closer look at theory and hypothesis to nail down what they mean.

What does theory mean?

As a noun, a theory is a group of tested general propositions “commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena .” This is what is known as a scientific   theory , which by definition is “an understanding that is based on already tested data or results .” Einstein’s theory of relativity and the  theory of evolution are both examples of such tested propositions .

Theory is also defined as a proposed explanation you might make about your own life and observations, and it’s one “whose status is still conjectural and subject to experimentation .” For example:  I’ve got my own theories about why he’s missing his deadlines all the time.  This example refers to an idea that has not yet been proven.

There are other uses of the word theory as well.

• In this example,  theory is “a body of principles or theorems belonging to one subject.” It can be a branch of science or art that deals with its principles or methods .
• For example: when she started to follow a new parenting theory based on a trendy book, it caused a conflict with her mother, who kept offering differing opinions .

First recorded in 1590–1600, theory originates from the Late Latin theōria , which stems from the Greek theōría. Synonyms for theory include approach , assumption , doctrine , ideology , method , philosophy , speculation , thesis , and understanding .

What does hypothesis mean?

Hypothesis is a noun that means “a proposition , or set of propositions, set forth as an explanation” that describe “some specified group of phenomena.” Sounds familiar to theory , no?

But, unlike a theory , a scientific  hypothesis is made before testing is done and isn’t based on results. Instead, it is the basis for further investigation . For example: her working hypothesis is that this new drug also has an unintended effect on the heart, and she is curious what the clinical trials  will show .

Hypothesis also refers to “a proposition assumed as a premise in an argument,” or “mere assumption or guess.” For example:

• She decided to drink more water for a week to test out her hypothesis that dehydration was causing her terrible headaches.
• After a night of her spouse’s maddening snoring, she came up with the hypothesis that sleeping on his back was exacerbating the problem.

Hypothesis was first recorded around 1590–1600 and originates from the Greek word hypóthesis (“basis, supposition”). Synonyms for hypothesis include: assumption , conclusion , conjecture , guess , inference , premise , theorem , and thesis .

How to use each

Although theory in terms of science is used to express something based on extensive research and experimentation, typically in everyday life, theory is used more casually to express an educated guess.

So in casual language,  theory and hypothesis are more likely to be used interchangeably to express an idea or speculation .

In most everyday uses, theory and hypothesis convey the same meaning. For example:

• Her opinion is just a theory , of course. She’s just guessing.
• Her opinion is just a hypothesis , of course. She’s just guessing.

It’s important to remember that a scientific   theory is different. It is based on tested results that support or substantiate it, whereas a hypothesis is formed before the research.

For example:

• His  hypothesis  for the class science project is that this brand of plant food is better than the rest for helping grass grow.
• After testing his hypothesis , he developed a new theory based on the experiment results: plant food B is actually more effective than plant food A in helping grass grow.

In these examples, theory “doesn’t mean a hunch or a guess,” according to Kenneth R. Miller, a cell biologist at Brown University. “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.”

So if you have a concept that is based on substantiated research, it’s a theory .

But if you’re working off of an assumption that you still need to test, it’s a hypothesis .

So remember, first comes a hypothesis , then comes theory . Now who’s ready for a  Big Bang Theory marathon?

Now that you’ve theorized and hypothesized through this whole article … keep testing your judgment (Or is it judgement?). Find out the correct spelling here!

Or find out the difference between these two common issues below!

WATCH: "Lethologica" vs. "Lethonomia": What's The Difference?

Go Behind The Words!

• By clicking "Sign Up", you are accepting Dictionary.com Terms & Conditions and Privacy policies.
• Comments This field is for validation purposes and should be left unchanged.

Commonly Confused

Hobbies & Passions

Word Origins

Current Events

[ er -y oo -dahyt ]

• Phone This field is for validation purposes and should be left unchanged.

Theories, Hypotheses, and Laws: Definitions, examples, and their roles in science

by Anthony Carpi, Ph.D., Anne E. Egger, Ph.D.

Listen to this reading

Did you know that the idea of evolution had been part of Western thought for more than 2,000 years before Charles Darwin was born? Like many theories, the theory of evolution was the result of the work of many different scientists working in different disciplines over a period of time.

A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and is logical, testable, and predictive.

As new evidence comes to light, or new interpretations of existing data are proposed, theories may be revised and even change; however, they are not tenuous or speculative.

A scientific hypothesis is an inferred explanation of an observation or research finding; while more exploratory in nature than a theory, it is based on existing scientific knowledge.

A scientific law is an expression of a mathematical or descriptive relationship observed in nature.

Imagine yourself shopping in a grocery store with a good friend who happens to be a chemist. Struggling to choose between the many different types of tomatoes in front of you, you pick one up, turn to your friend, and ask her if she thinks the tomato is organic . Your friend simply chuckles and replies, "Of course it's organic!" without even looking at how the fruit was grown. Why the amused reaction? Your friend is highlighting a simple difference in vocabulary. To a chemist, the term organic refers to any compound in which hydrogen is bonded to carbon. Tomatoes (like all plants) are abundant in organic compounds – thus your friend's laughter. In modern agriculture, however, organic has come to mean food items grown or raised without the use of chemical fertilizers, pesticides, or other additives.

So who is correct? You both are. Both uses of the word are correct, though they mean different things in different contexts. There are, of course, lots of words that have more than one meaning (like bat , for example), but multiple meanings can be especially confusing when two meanings convey very different ideas and are specific to one field of study.

• Scientific theories

The term theory also has two meanings, and this double meaning often leads to confusion. In common language, the term theory generally refers to speculation or a hunch or guess. You might have a theory about why your favorite sports team isn't playing well, or who ate the last cookie from the cookie jar. But these theories do not fit the scientific use of the term. In science, a theory is a well-substantiated and comprehensive set of ideas that explains a phenomenon in nature. A scientific theory is based on large amounts of data and observations that have been collected over time. Scientific theories can be tested and refined by additional research , and they allow scientists to make predictions. Though you may be correct in your hunch, your cookie jar conjecture doesn't fit this more rigorous definition.

All scientific disciplines have well-established, fundamental theories . For example, atomic theory describes the nature of matter and is supported by multiple lines of evidence from the way substances behave and react in the world around us (see our series on Atomic Theory ). Plate tectonic theory describes the large scale movement of the outer layer of the Earth and is supported by evidence from studies about earthquakes , magnetic properties of the rocks that make up the seafloor , and the distribution of volcanoes on Earth (see our series on Plate Tectonic Theory ). The theory of evolution by natural selection , which describes the mechanism by which inherited traits that affect survivability or reproductive success can cause changes in living organisms over generations , is supported by extensive studies of DNA , fossils , and other types of scientific evidence (see our Charles Darwin series for more information). Each of these major theories guides and informs modern research in those fields, integrating a broad, comprehensive set of ideas.

So how are these fundamental theories developed, and why are they considered so well supported? Let's take a closer look at some of the data and research supporting the theory of natural selection to better see how a theory develops.

Comprehension Checkpoint

• The development of a scientific theory: Evolution and natural selection

The theory of evolution by natural selection is sometimes maligned as Charles Darwin 's speculation on the origin of modern life forms. However, evolutionary theory is not speculation. While Darwin is rightly credited with first articulating the theory of natural selection, his ideas built on more than a century of scientific research that came before him, and are supported by over a century and a half of research since.

• The Fixity Notion: Linnaeus

Figure 1: Cover of the 1760 edition of Systema Naturae .

Research about the origins and diversity of life proliferated in the 18th and 19th centuries. Carolus Linnaeus , a Swedish botanist and the father of modern taxonomy (see our module Taxonomy I for more information), was a devout Christian who believed in the concept of Fixity of Species , an idea based on the biblical story of creation. The Fixity of Species concept said that each species is based on an ideal form that has not changed over time. In the early stages of his career, Linnaeus traveled extensively and collected data on the structural similarities and differences between different species of plants. Noting that some very different plants had similar structures, he began to piece together his landmark work, Systema Naturae, in 1735 (Figure 1). In Systema , Linnaeus classified organisms into related groups based on similarities in their physical features. He developed a hierarchical classification system , even drawing relationships between seemingly disparate species (for example, humans, orangutans, and chimpanzees) based on the physical similarities that he observed between these organisms. Linnaeus did not explicitly discuss change in organisms or propose a reason for his hierarchy, but by grouping organisms based on physical characteristics, he suggested that species are related, unintentionally challenging the Fixity notion that each species is created in a unique, ideal form.

• The age of Earth: Leclerc and Hutton

Also in the early 1700s, Georges-Louis Leclerc, a French naturalist, and James Hutton , a Scottish geologist, began to develop new ideas about the age of the Earth. At the time, many people thought of the Earth as 6,000 years old, based on a strict interpretation of the events detailed in the Christian Old Testament by the influential Scottish Archbishop Ussher. By observing other planets and comets in the solar system , Leclerc hypothesized that Earth began as a hot, fiery ball of molten rock, mostly consisting of iron. Using the cooling rate of iron, Leclerc calculated that Earth must therefore be at least 70,000 years old in order to have reached its present temperature.

Hutton approached the same topic from a different perspective, gathering observations of the relationships between different rock formations and the rates of modern geological processes near his home in Scotland. He recognized that the relatively slow processes of erosion and sedimentation could not create all of the exposed rock layers in only a few thousand years (see our module The Rock Cycle ). Based on his extensive collection of data (just one of his many publications ran to 2,138 pages), Hutton suggested that the Earth was far older than human history – hundreds of millions of years old.

While we now know that both Leclerc and Hutton significantly underestimated the age of the Earth (by about 4 billion years), their work shattered long-held beliefs and opened a window into research on how life can change over these very long timescales.

• Fossil studies lead to the development of a theory of evolution: Cuvier

Figure 2: Illustration of an Indian elephant jaw and a mammoth jaw from Cuvier's 1796 paper.

With the age of Earth now extended by Leclerc and Hutton, more researchers began to turn their attention to studying past life. Fossils are the main way to study past life forms, and several key studies on fossils helped in the development of a theory of evolution . In 1795, Georges Cuvier began to work at the National Museum in Paris as a naturalist and anatomist. Through his work, Cuvier became interested in fossils found near Paris, which some claimed were the remains of the elephants that Hannibal rode over the Alps when he invaded Rome in 218 BCE . In studying both the fossils and living species , Cuvier documented different patterns in the dental structure and number of teeth between the fossils and modern elephants (Figure 2) (Horner, 1843). Based on these data , Cuvier hypothesized that the fossil remains were not left by Hannibal, but were from a distinct species of animal that once roamed through Europe and had gone extinct thousands of years earlier: the mammoth. The concept of species extinction had been discussed by a few individuals before Cuvier, but it was in direct opposition to the Fixity of Species concept – if every organism were based on a perfectly adapted, ideal form, how could any cease to exist? That would suggest it was no longer ideal.

While his work provided critical evidence of extinction , a key component of evolution , Cuvier was highly critical of the idea that species could change over time. As a result of his extensive studies of animal anatomy, Cuvier had developed a holistic view of organisms , stating that the

number, direction, and shape of the bones that compose each part of an animal's body are always in a necessary relation to all the other parts, in such a way that ... one can infer the whole from any one of them ...

In other words, Cuvier viewed each part of an organism as a unique, essential component of the whole organism. If one part were to change, he believed, the organism could not survive. His skepticism about the ability of organisms to change led him to criticize the whole idea of evolution , and his prominence in France as a scientist played a large role in discouraging the acceptance of the idea in the scientific community.

• Studies of invertebrates support a theory of change in species: Lamarck

Jean Baptiste Lamarck, a contemporary of Cuvier's at the National Museum in Paris, studied invertebrates like insects and worms. As Lamarck worked through the museum's large collection of invertebrates, he was impressed by the number and variety of organisms . He became convinced that organisms could, in fact, change through time, stating that

... time and favorable conditions are the two principal means which nature has employed in giving existence to all her productions. We know that for her time has no limit, and that consequently she always has it at her disposal.

This was a radical departure from both the fixity concept and Cuvier's ideas, and it built on the long timescale that geologists had recently established. Lamarck proposed that changes that occurred during an organism 's lifetime could be passed on to their offspring, suggesting, for example, that a body builder's muscles would be inherited by their children.

As it turned out, the mechanism by which Lamarck proposed that organisms change over time was wrong, and he is now often referred to disparagingly for his "inheritance of acquired characteristics" idea. Yet despite the fact that some of his ideas were discredited, Lamarck established a support for evolutionary theory that others would build on and improve.

• Rock layers as evidence for evolution: Smith

In the early 1800s, a British geologist and canal surveyor named William Smith added another component to the accumulating evidence for evolution . Smith observed that rock layers exposed in different parts of England bore similarities to one another: These layers (or strata) were arranged in a predictable order, and each layer contained distinct groups of fossils . From this series of observations , he developed a hypothesis that specific groups of animals followed one another in a definite sequence through Earth's history, and this sequence could be seen in the rock layers. Smith's hypothesis was based on his knowledge of geological principles , including the Law of Superposition.

The Law of Superposition states that sediments are deposited in a time sequence, with the oldest sediments deposited first, or at the bottom, and newer layers deposited on top. The concept was first expressed by the Persian scientist Avicenna in the 11th century, but was popularized by the Danish scientist Nicolas Steno in the 17th century. Note that the law does not state how sediments are deposited; it simply describes the relationship between the ages of deposited sediments.

Figure 3: Engraving from William Smith's 1815 monograph on identifying strata by fossils.

Smith backed up his hypothesis with extensive drawings of fossils uncovered during his research (Figure 3), thus allowing other scientists to confirm or dispute his findings. His hypothesis has, in fact, been confirmed by many other scientists and has come to be referred to as the Law of Faunal Succession. His work was critical to the formation of evolutionary theory as it not only confirmed Cuvier's work that organisms have gone extinct , but it also showed that the appearance of life does not date to the birth of the planet. Instead, the fossil record preserves a timeline of the appearance and disappearance of different organisms in the past, and in doing so offers evidence for change in organisms over time.

• The theory of evolution by natural selection: Darwin and Wallace

It was into this world that Charles Darwin entered: Linnaeus had developed a taxonomy of organisms based on their physical relationships, Leclerc and Hutton demonstrated that there was sufficient time in Earth's history for organisms to change, Cuvier showed that species of organisms have gone extinct , Lamarck proposed that organisms change over time, and Smith established a timeline of the appearance and disappearance of different organisms in the geological record .

Figure 4: Title page of the 1859 Murray edition of the Origin of Species by Charles Darwin.

Charles Darwin collected data during his work as a naturalist on the HMS Beagle starting in 1831. He took extensive notes on the geology of the places he visited; he made a major find of fossils of extinct animals in Patagonia and identified an extinct giant ground sloth named Megatherium . He experienced an earthquake in Chile that stranded beds of living mussels above water, where they would be preserved for years to come.

Perhaps most famously, he conducted extensive studies of animals on the Galápagos Islands, noting subtle differences in species of mockingbird, tortoise, and finch that were isolated on different islands with different environmental conditions. These subtle differences made the animals highly adapted to their environments .

This broad spectrum of data led Darwin to propose an idea about how organisms change "by means of natural selection" (Figure 4). But this idea was not based only on his work, it was also based on the accumulation of evidence and ideas of many others before him. Because his proposal encompassed and explained many different lines of evidence and previous work, they formed the basis of a new and robust scientific theory regarding change in organisms – the theory of evolution by natural selection .

Darwin's ideas were grounded in evidence and data so compelling that if he had not conceived them, someone else would have. In fact, someone else did. Between 1858 and 1859, Alfred Russel Wallace , a British naturalist, wrote a series of letters to Darwin that independently proposed natural selection as the means for evolutionary change. The letters were presented to the Linnean Society of London, a prominent scientific society at the time (see our module on Scientific Institutions and Societies ). This long chain of research highlights that theories are not just the work of one individual. At the same time, however, it often takes the insight and creativity of individuals to put together all of the pieces and propose a new theory . Both Darwin and Wallace were experienced naturalists who were familiar with the work of others. While all of the work leading up to 1830 contributed to the theory of evolution , Darwin's and Wallace's theory changed the way that future research was focused by presenting a comprehensive, well-substantiated set of ideas, thus becoming a fundamental theory of biological research.

• Expanding, testing, and refining scientific theories
• Genetics and evolution: Mendel and Dobzhansky

Since Darwin and Wallace first published their ideas, extensive research has tested and expanded the theory of evolution by natural selection . Darwin had no concept of genes or DNA or the mechanism by which characteristics were inherited within a species . A contemporary of Darwin's, the Austrian monk Gregor Mendel , first presented his own landmark study, Experiments in Plant Hybridization, in 1865 in which he provided the basic patterns of genetic inheritance , describing which characteristics (and evolutionary changes) can be passed on in organisms (see our Genetics I module for more information). Still, it wasn't until much later that a "gene" was defined as the heritable unit.

In 1937, the Ukrainian born geneticist Theodosius Dobzhansky published Genetics and the Origin of Species , a seminal work in which he described genes themselves and demonstrated that it is through mutations in genes that change occurs. The work defined evolution as "a change in the frequency of an allele within a gene pool" ( Dobzhansky, 1982 ). These studies and others in the field of genetics have added to Darwin's work, expanding the scope of the theory .

• Evolution under a microscope: Lenski

More recently, Dr. Richard Lenski, a scientist at Michigan State University, isolated a single Escherichia coli bacterium in 1989 as the first step of the longest running experimental test of evolutionary theory to date – a true test meant to replicate evolution and natural selection in the lab.

After the single microbe had multiplied, Lenski isolated the offspring into 12 different strains , each in their own glucose-supplied culture, predicting that the genetic make-up of each strain would change over time to become more adapted to their specific culture as predicted by evolutionary theory . These 12 lines have been nurtured for over 40,000 bacterial generations (luckily bacterial generations are much shorter than human generations) and exposed to different selective pressures such as heat , cold, antibiotics, and infection with other microorganisms. Lenski and colleagues have studied dozens of aspects of evolutionary theory with these genetically isolated populations . In 1999, they published a paper that demonstrated that random genetic mutations were common within the populations and highly diverse across different individual bacteria . However, "pivotal" mutations that are associated with beneficial changes in the group are shared by all descendants in a population and are much rarer than random mutations, as predicted by the theory of evolution by natural selection (Papadopoulos et al., 1999).

• Punctuated equilibrium: Gould and Eldredge

While established scientific theories like evolution have a wealth of research and evidence supporting them, this does not mean that they cannot be refined as new information or new perspectives on existing data become available. For example, in 1972, biologist Stephen Jay Gould and paleontologist Niles Eldredge took a fresh look at the existing data regarding the timing by which evolutionary change takes place. Gould and Eldredge did not set out to challenge the theory of evolution; rather they used it as a guiding principle and asked more specific questions to add detail and nuance to the theory. This is true of all theories in science: they provide a framework for additional research. At the time, many biologists viewed evolution as occurring gradually, causing small incremental changes in organisms at a relatively steady rate. The idea is referred to as phyletic gradualism , and is rooted in the geological concept of uniformitarianism . After reexamining the available data, Gould and Eldredge came to a different explanation, suggesting that evolution consists of long periods of stability that are punctuated by occasional instances of dramatic change – a process they called punctuated equilibrium .

Like Darwin before them, their proposal is rooted in evidence and research on evolutionary change, and has been supported by multiple lines of evidence. In fact, punctuated equilibrium is now considered its own theory in evolutionary biology. Punctuated equilibrium is not as broad of a theory as natural selection . In science, some theories are broad and overarching of many concepts, such as the theory of evolution by natural selection; others focus on concepts at a smaller, or more targeted, scale such as punctuated equilibrium. And punctuated equilibrium does not challenge or weaken the concept of natural selection; rather, it represents a change in our understanding of the timing by which change occurs in organisms , and a theory within a theory. The theory of evolution by natural selection now includes both gradualism and punctuated equilibrium to describe the rate at which change proceeds.

• Hypotheses and laws: Other scientific concepts

One of the challenges in understanding scientific terms like theory is that there is not a precise definition even within the scientific community. Some scientists debate over whether certain proposals merit designation as a hypothesis or theory , and others mistakenly use the terms interchangeably. But there are differences in these terms. A hypothesis is a proposed explanation for an observable phenomenon. Hypotheses , just like theories , are based on observations from research . For example, LeClerc did not hypothesize that Earth had cooled from a molten ball of iron as a random guess; rather, he developed this hypothesis based on his observations of information from meteorites.

A scientist often proposes a hypothesis before research confirms it as a way of predicting the outcome of study to help better define the parameters of the research. LeClerc's hypothesis allowed him to use known parameters (the cooling rate of iron) to do additional work. A key component of a formal scientific hypothesis is that it is testable and falsifiable. For example, when Richard Lenski first isolated his 12 strains of bacteria , he likely hypothesized that random mutations would cause differences to appear within a period of time in the different strains of bacteria. But when a hypothesis is generated in science, a scientist will also make an alternative hypothesis , an explanation that explains a study if the data do not support the original hypothesis. If the different strains of bacteria in Lenski's work did not diverge over the indicated period of time, perhaps the rate of mutation was slower than first thought.

So you might ask, if theories are so well supported, do they eventually become laws? The answer is no – not because they aren't well-supported, but because theories and laws are two very different things. Laws describe phenomena, often mathematically. Theories, however, explain phenomena. For example, in 1687 Isaac Newton proposed a Theory of Gravitation, describing gravity as a force of attraction between two objects. As part of this theory, Newton developed a Law of Universal Gravitation that explains how this force operates. This law states that the force of gravity between two objects is inversely proportional to the square of the distance between those objects. Newton 's Law does not explain why this is true, but it describes how gravity functions (see our Gravity: Newtonian Relationships module for more detail). In 1916, Albert Einstein developed his theory of general relativity to explain the mechanism by which gravity has its effect. Einstein's work challenges Newton's theory, and has been found after extensive testing and research to more accurately describe the phenomenon of gravity. While Einstein's work has replaced Newton's as the dominant explanation of gravity in modern science, Newton's Law of Universal Gravitation is still used as it reasonably (and more simply) describes the force of gravity under many conditions. Similarly, the Law of Faunal Succession developed by William Smith does not explain why organisms follow each other in distinct, predictable ways in the rock layers, but it accurately describes the phenomenon.

Theories, hypotheses , and laws drive scientific progress

Theories, hypotheses , and laws are not simply important components of science, they drive scientific progress. For example, evolutionary biology now stands as a distinct field of science that focuses on the origins and descent of species . Geologists now rely on plate tectonics as a conceptual model and guiding theory when they are studying processes at work in Earth's crust . And physicists refer to atomic theory when they are predicting the existence of subatomic particles yet to be discovered. This does not mean that science is "finished," or that all of the important theories have been discovered already. Like evolution , progress in science happens both gradually and in short, dramatic bursts. Both types of progress are critical for creating a robust knowledge base with data as the foundation and scientific theories giving structure to that knowledge.

Table of Contents

• Theories, hypotheses, and laws drive scientific progress

Activate glossary term highlighting to easily identify key terms within the module. Once highlighted, you can click on these terms to view their definitions.

Activate NGSS annotations to easily identify NGSS standards within the module. Once highlighted, you can click on them to view these standards.

The Difference Between a Scientific Hypothesis, Theory, and Law

Let’s address some common misconceptions about the basic concepts of science..

Totojang/iStock

Nobody is exempt from misunderstanding scientific concepts and/or applying them incorrectly. Statistics from the National Science Board show that Americans scored an average of 5.6 over 9 true-or-false and multiple-choice science-related questions in 2016. Because of the low number of questions, the study is better at differentiating low and medium levels of knowledge than those with higher levels of knowledge. However, the r esults weren’t much different in previous studies, suggesting that Americans generally have had the same basic levels of science literacy since the beginning of the century.

In this context, we’d like to clear up and emphasize the distinctions between scientific hypothesis, theory, and law, and why you shouldn’t use these terms interchangeably. 

Hypothesis: the core of the scientific method

The scientific method is an empirical procedure that consists of systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.  It’s a process that’s meant to ensure that the collection of evidence, results, and conclusions are not biased by subjective views and can be repeated consistently by others.

Although there might be variations due to the requirements of each branch of science, the steps of the scientific method are more or less the same.

The scientific method often starts with an observation or asking a question, such as the observation of certain natural phenomena or asking why a particular phenomenon exists or why it occurs in a particular way.

Observation motivates a question and the question motivates an initial hypothesis. The initial hypothesis is a conjecture that works as a temporary answer to the question, formulated via induction on the basis of what’s been observed. 

To better understand this, let’s take the case of physician Ignaz Semmelweis. In mid-19th Century, he worked at the First Obstetrical Clinic of Vienna General Hospital, where 10% of women in labor died due to puerperal fever. Meanwhile, the Second Obstetrical Clinic had an average maternal mortality rate of 4%. Semmelweis asked himself why there was a discrepancy in mortality rates between the two clinics. 

  Through observation, he determined and eliminated a number of differences between the two clinics. Because the techniques, climate, etc., were pretty much the same in both places, he ended up concluding that it had something to do with the health workers who helped women in labor. In the Second Clinic, births were attended only by midwives, while in the First Clinic, births were often attended by medical students who also performed autopsies. Semmelweis came up with the hypothesis that medical students spread “cadaveric contamination” in the First Clinic and this was causing the puerperal fever. 

He ordered all medical students to wash their hands with chlorinated lime after performing autopsies, and the mortality rate in the First Clinic decreased by 90%. 

Semmelweis is considered one of the early pioneers of antiseptic procedures .

This story doesn’t only demonstrate the importance of the initial hypothesis, but also the importance of testing it through experiments, field studies, observational studies, or other experimental work. In fact, this is the next step in the scientific method, and it’s essential to draw conclusions. 

Theory: the Why and How of natural phenomena

A scientific theory can be defined as a series of repeatedly tested and verified hypotheses and concepts. Scientific theories are based on hypotheses that are constructed and tested using the scientific method, and which may bring together a number of facts and hypotheses.

A theory synthesizes the discovered facts about phenomena in a way that allows scientists to formulate predictions and develop new hypotheses. For example, we can hypothesize the reasons why an animal looks or acts in a certain way based on Darwin’s theory of evolution. Or we can predict that antiseptics will prevent diseases if we take into account the germ theory . The confirmation of these hypotheses and predictions reinforces the theories they’re based on.

For a theory to be valid, it must be testable, hold true for general tendencies and not only to specific cases, and it must not contradict verified pre-existing theories and laws. 

Law: the patterns of nature

In general, a scientific law is  the description of an observed phenomenon. It doesn’t explain why the phenomenon exists or what causes it. Laws can be thought of as the starting place, the point from where questions like “why” and “how” are asked.

For example, we can throw a ball under certain conditions and predict its movement by taking into account Newton’s laws of motion . These laws do not only involve several statements but also equations and formulas.  However, while Newton’s laws might mathematically describe how two bodies interact with each other, they don’t explain what gravity is, or how it works. 

Contrary to popular belief, scientific laws are not immutable. They must be universal and absolute to qualify as laws, but they can be corrected or extended to make them more accurate. For example, Euler’s laws of motion amplify Newton’s laws of motion to rigid bodies ,  and how gravity works was only understood in more detail when Albert Einstein developed the Theory of Relativity.

RECOMMENDED ARTICLES

Common misconceptions about scientific laws, theories, and hypotheses.

• There is a hierarchy between laws, theories, and hypotheses: Some people think that hypotheses “evolve” into theories and theories “evolve” into laws. While a number of verified hypotheses can be included in a theory, it’s never only one. And theories do not turn into scientific laws because they’re simply different concepts. As stated above, theories explain phenomena and laws reflect patterns. 

You don’t have to be a scientist to understand scientific terms. In the information era, scientific concepts surround us, but even if access to knowledge is easier than ever nowadays, there are still a lot of misconceptions around. It’s always better to be on the safe side and getting your facts straight. 

The Blueprint Daily

Stay up-to-date on engineering, tech, space, and science news with The Blueprint.

By clicking sign up, you confirm that you accept this site's Terms of Use and Privacy Policy

ABOUT THE EDITOR

Maia Mulko Maia is a bilingual freelance writer and copywriter with a degree in Communication Studies. Although she has written for several different niches and publications, she spent most of her career writing for Descentralizar, a Spanish publication that investigates stories at the intersection of technology and society. She has also written scripts for a wide variety of science-related YouTube channels. Maia&nbsp;is particularly interested in space, AI, mobility, gaming, robotics, and assistive technologies.&nbsp;

POPULAR ARTICLES

Forget conventional electronics, dna tech stores data, offers computing functions, 200 martian meteorites on earth came from just 5 craters, claim scientists, sound weaves unlikely bond between metal, wood in a 3d printing breakthrough, saving albatross: south africa to ‘bomb’ remote island to eradicate mice, related articles.

Deadly land-sea ‘tag team’ caused marine mass extinction 185 million years ago

Polaris Dawn in the dusk? Falcon 9 rocket crash may shake up SpaceX plans

Farmer finds ‘extremely rare’ fossil of sea cow slaughtered by shark-croc team

24-mile range, 115 mph: US Army buys $1B worth of Switchblade kamikaze drones

• Key Differences

Know the Differences & Comparisons

Difference Between Hypothesis and Theory

The term ‘hypothesis’ is often contrasted with the term theory which implies an idea, typically proven, which aims at explaining facts and events. Both hypothesis and theory are important components of developing an approach, but these are not same. There exist a fine line of difference between hypothesis and theory, discussed in this article, have a look.

Content: Hypothesis Vs Theory

Comparison chart.

Definition of Hypothesis

An unproven statement or a mere assumption to be proved or disproved, about a factor, on which the researcher is interested, is called a hypothesis. It is a tentative statement, which is concerned with the relationship between two or more phenomena, as specified by the theoretical framework. The hypothesis has to go through a test, to determine its validity.

In other words, the hypothesis is a predictive statement, which can be objectively verified and tested through scientific methods, and relates the independent factor to the dependent one. To a researcher, a hypothesis is more like a question which he intends to resolve. The salient features of hypothesis are:

• It must be clear and precise or else the reliability of the inferences drawn will be questioned.
• It can be put to the test.
• If the hypothesis is relational, it should state the relationship between independent and dependent variables.
• The hypothesis should be open and responsive to testing within the stipulated time.
• It should be limited in scope and must be clearly defined.

Definition of Theory

An idea or a broad range of ideas that are assumed to be true, which aims at explaining cause and effect relationship between multiple observed phenomena. It is based on hypothesis, which after a thorough analysis and continuous testing and confirmation through observation and experiments, becomes a theory. As it is backed by evidence, it is scientifically proven.

Just like hypothesis, theories can also be accepted or rejected. As more and more information is gathered on the subject, theories are modified accordingly, to increase the accuracy of prediction over time.

Key Differences Between Hypothesis and Theory

The points given below are vital, so far as the difference between hypothesis and theory is concerned:

• Hypothesis refers to a supposition, based on few pieces of evidence, as an inception of further research or investigation. A theory is a well-affirmed explanation of natural phenomena, which is frequently validated through experimentation and observation.
• While the hypothesis is based on a little amount of data, the theory is based on a wide set of data.
• The hypothesis is an unproven statement; that can be tested. On the other hand, the theory is a scientifically tested and proven explanation of fact or event.
• Hypothesis relies on suggestions, prediction, possibility or projects whereas a theory is supported by evidence and is verified.
• The hypothesis may or may not be proved true, so the result is uncertain. On the contrary, the theory is one, that is assumed to be true and so its result is certain.
• Hypothesis and theory are two levels of the scientific method, i.e. theory follows hypothesis and the basis for research is hypothesis whose outcome is a theory.

Both hypothesis and theory are testable and falsifiable. When a hypothesis is proved true, by passing all critical tests and analysis, it becomes a theory. So, the hypothesis is very different from theory, as the former is something unproven but the latter is a proven and tested statement.

You Might Also Like:

BELLENS MOTEBEJANE says

July 15, 2019 at 2:31 pm

AMAIZING !WHAT ARE THE DIFFERENCE BETWEEN THEORY AND LAW?

February 17, 2022 at 3:47 am

Thanks, I’m finally clear on this for the first time in my life of 65 years

Curtis Le Gendre says

September 14, 2022 at 8:02 am

Great Information

Kenneth says

November 19, 2022 at 2:10 am

I was looking for some takes on this topic, and I found your article quite informative. It has given me a fresh perspective on the topic tackled. Thanks!

Stefanie Banis says

February 9, 2024 at 6:35 pm

Very informative! Thank you! I understand the difference much better now!

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.

• 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

Discussion with Kara Rogers of how the scientific model is used to test a hypothesis or represent a theory

What is a scientific hypothesis?

It's the initial building block in the scientific method.

Hypothesis basics

What makes a hypothesis testable.

• Types of hypotheses
• Hypothesis versus theory

Additional resources

Bibliography.

A scientific hypothesis is a tentative, testable explanation for a phenomenon in the natural world. It's the initial building block in the scientific method . Many describe it as an "educated guess" based on prior knowledge and observation. While this is true, a hypothesis is more informed than a guess. While an "educated guess" suggests a random prediction based on a person's expertise, developing a hypothesis requires active observation and background research. 

The basic idea of a hypothesis is that there is no predetermined outcome. For a solution to be termed a scientific hypothesis, it has to be an idea that can be supported or refuted through carefully crafted experimentation or observation. This concept, called falsifiability and testability, was advanced in the mid-20th century by Austrian-British philosopher Karl Popper in his famous book "The Logic of Scientific Discovery" (Routledge, 1959).

A key function of a hypothesis is to derive predictions about the results of future experiments and then perform those experiments to see whether they support the predictions.

A hypothesis is usually written in the form of an if-then statement, which gives a possibility (if) and explains what may happen because of the possibility (then). The statement could also include "may," according to California State University, Bakersfield .

Here are some examples of hypothesis statements:

• If garlic repels fleas, then a dog that is given garlic every day will not get fleas.
• If sugar causes cavities, then people who eat a lot of candy may be more prone to cavities.
• If ultraviolet light can damage the eyes, then maybe this light can cause blindness.

A useful hypothesis should be testable and falsifiable. That means that it should be possible to prove it wrong. A theory that can't be proved wrong is nonscientific, according to Karl Popper's 1963 book " Conjectures and Refutations ."

An example of an untestable statement is, "Dogs are better than cats." That's because the definition of "better" is vague and subjective. However, an untestable statement can be reworded to make it testable. For example, the previous statement could be changed to this: "Owning a dog is associated with higher levels of physical fitness than owning a cat." With this statement, the researcher can take measures of physical fitness from dog and cat owners and compare the two.

Types of scientific hypotheses

In an experiment, researchers generally state their hypotheses in two ways. The null hypothesis predicts that there will be no relationship between the variables tested, or no difference between the experimental groups. The alternative hypothesis predicts the opposite: that there will be a difference between the experimental groups. This is usually the hypothesis scientists are most interested in, according to the University of Miami .

For example, a null hypothesis might state, "There will be no difference in the rate of muscle growth between people who take a protein supplement and people who don't." The alternative hypothesis would state, "There will be a difference in the rate of muscle growth between people who take a protein supplement and people who don't."

If the results of the experiment show a relationship between the variables, then the null hypothesis has been rejected in favor of the alternative hypothesis, according to the book " Research Methods in Psychology " (​​BCcampus, 2015). 

There are other ways to describe an alternative hypothesis. The alternative hypothesis above does not specify a direction of the effect, only that there will be a difference between the two groups. That type of prediction is called a two-tailed hypothesis. If a hypothesis specifies a certain direction — for example, that people who take a protein supplement will gain more muscle than people who don't — it is called a one-tailed hypothesis, according to William M. K. Trochim , a professor of Policy Analysis and Management at Cornell University.

Sometimes, errors take place during an experiment. These errors can happen in one of two ways. A type I error is when the null hypothesis is rejected when it is true. This is also known as a false positive. A type II error occurs when the null hypothesis is not rejected when it is false. This is also known as a false negative, according to the University of California, Berkeley . 

A hypothesis can be rejected or modified, but it can never be proved correct 100% of the time. For example, a scientist can form a hypothesis stating that if a certain type of tomato has a gene for red pigment, that type of tomato will be red. During research, the scientist then finds that each tomato of this type is red. Though the findings confirm the hypothesis, there may be a tomato of that type somewhere in the world that isn't red. Thus, the hypothesis is true, but it may not be true 100% of the time.

Scientific theory vs. scientific hypothesis

The best hypotheses are simple. They deal with a relatively narrow set of phenomena. But theories are broader; they generally combine multiple hypotheses into a general explanation for a wide range of phenomena, according to the University of California, Berkeley . For example, a hypothesis might state, "If animals adapt to suit their environments, then birds that live on islands with lots of seeds to eat will have differently shaped beaks than birds that live on islands with lots of insects to eat." After testing many hypotheses like these, Charles Darwin formulated an overarching theory: the theory of evolution by natural selection.

"Theories are the ways that we make sense of what we observe in the natural world," Tanner said. "Theories are structures of ideas that explain and interpret facts." 

• Read more about writing a hypothesis, from the American Medical Writers Association.
• Find out why a hypothesis isn't always necessary in science, from The American Biology Teacher.
• Learn about null and alternative hypotheses, from Prof. Essa on YouTube .

Encyclopedia Britannica. Scientific Hypothesis. Jan. 13, 2022. https://www.britannica.com/science/scientific-hypothesis

Karl Popper, "The Logic of Scientific Discovery," Routledge, 1959.

California State University, Bakersfield, "Formatting a testable hypothesis." https://www.csub.edu/~ddodenhoff/Bio100/Bio100sp04/formattingahypothesis.htm  

Karl Popper, "Conjectures and Refutations," Routledge, 1963.

Price, P., Jhangiani, R., & Chiang, I., "Research Methods of Psychology — 2nd Canadian Edition," BCcampus, 2015.‌

University of Miami, "The Scientific Method" http://www.bio.miami.edu/dana/161/evolution/161app1_scimethod.pdf  

William M.K. Trochim, "Research Methods Knowledge Base," https://conjointly.com/kb/hypotheses-explained/  

University of California, Berkeley, "Multiple Hypothesis Testing and False Discovery Rate" https://www.stat.berkeley.edu/~hhuang/STAT141/Lecture-FDR.pdf  

University of California, Berkeley, "Science at multiple levels" https://undsci.berkeley.edu/article/0_0_0/howscienceworks_19

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Large patch of the Atlantic Ocean near the equator has been cooling at record speeds — and scientists can't figure out why

Earth from space: Massive landslide dams Canadian river, trapping endangered fish on the wrong side

Ancient sea cow was killed by prehistoric croc then torn apart by a tiger shark

Most Popular

• 2 For C. diff, antibiotic resistance comes at a cost
• 3 Large patch of the Atlantic Ocean near the equator has been cooling at record speeds — and scientists can't figure out why
• 4 Gravitational waves hint at a 'supercool' secret about the Big Bang
• 5 New reactor could more than triple the yield of one of the world's most valuable chemicals

• Biology Difference Between
• Difference Between Hypothesis And Theory

Difference Between Theory and Hypothesis

Many of them belittle evolution because “it is just a theory.” Gravity, on the other hand, must be real because it is a law. The words “theory,” “facts,” “laws” and “hypothesis” have a very specific meaning in the scientific world that doesn’t quite match the ones we use in everyday language. A hypothesis is a tentative explanation of an observation that can be tested. It acts as a starting point for further explanation. Theory, on the other hand, is an explanation of some aspect of the natural world that’s well-justified by facts, tested hypotheses, and laws. Let us look at more differences between hypothesis and theory given in a tabular column below.

Theory vs Hypothesis

From the above differences, we can infer that a hypothesis might change significantly as the testing occurs. A hypothesis can either be right or wrong. When a hypothesis is tested and proved true, it becomes a theory. At BYJU’S, learn more differences like the difference between asteroid and comet.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

Visit BYJU’S for all Biology related queries and study materials

Your result is as below

Request OTP on Voice Call

Leave a Comment Cancel reply

Your Mobile number and Email id will not be published. Required fields are marked *

Post My Comment

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Hypothesis vs. Theory: Understanding the Differences

“Hypothesis” and “theory” are two terms often used in science, but they have different meanings. Understanding the distinction between these two words can help us make sense of scientific explanations. In this article, we will explore the differences between “hypothesis” and “theory” in a way that is easy to understand. By the end, you’ll have a clearer grasp of these concepts and be able to use them confidently in scientific discussions.

Hypothesis vs. Theory

• A  hypothesis  is a preliminary assumption to be tested.
• A  theory  is a well-supported explanation for a broad range of phenomena.

Hypothesis vs. Theory: The Definition

What does hypothesis mean.

A hypothesis is a proposed explanation for a phenomenon or a scientific question that can be tested through experimentation or observation. It is an essential part of the scientific method, which involves formulating a hypothesis, conducting experiments to test it, and analyzing the results to draw conclusions.

In scientific research, a hypothesis serves as a tentative solution to a problem or a preliminary explanation for an observed phenomenon. It is based on existing knowledge and is formulated to be tested and potentially refuted through empirical evidence. A well-constructed hypothesis is specific, testable, and falsifiable, meaning that it can be proven false through experimentation or observation.

• Example of a hypothesis : “If a person consumes more vitamin C, then their immune system will be stronger and they will have a lower likelihood of catching a cold.”

What Does Theory Mean?

A theory is a well-substantiated explanation of some aspect of the natural world that is based on a body of evidence, observations, and experimentation. In the scientific context, a theory is more than just a guess or a hypothesis; it is a comprehensive framework that has been rigorously tested and supported by a substantial amount of empirical data.

Scientific theories are developed through the scientific method, which involves formulating hypotheses, conducting experiments, and analyzing the results. As evidence accumulates and supports a particular explanation, it may be elevated to the status of a theory. Importantly, scientific theories are not static or unchangeable; they are subject to modification or even rejection in light of new evidence or more comprehensive explanations.

• Example of a theory: The theory of evolution, which explains how species change over time through the process of natural selection.

Hypothesis vs. Theory: Usage

You employ  hypotheses  during the early stages of research to develop experiments. For instance, you might hypothesize that a plant given more sunlight will grow faster.

A  theory , like the Theory of Evolution, summarizes a group of tested hypotheses and facts to explain a complex set of patterns and behaviors.

For a better understanding of the differences between the two terms, let’s take a look at the table below:

Tips to Remember the Differences

• Think of a  hypothesis  as a  “hunch”  to be tested.
• View a  theory  as a  “tapestry”  of well-tested ideas.
• Use the phrase  “hypothesis for testing”  and  “theory for explaining”  to keep them distinct in your mind.

Hypothesis vs. Theory: Examples

Example sentences using hypothesis.

• She formulated a  hypothesis  to explain the observed pattern in the data.
• The researchers tested their  hypothesis  through a series of carefully controlled experiments.
• The  hypothesis  proposed by the scientist led to a new understanding of the chemical reaction.
• It is essential to develop a clear and testable  hypothesis  before conducting the research.
• The  hypothesis  was supported by the experimental results, providing valuable insights into the phenomenon.

Example Sentences Using Theory

• Einstein ‘s  theory of relativity has fundamentally altered our understanding of space and time.
• Darwin’s theory of natural selection provides a framework for understanding the evolution of species.
• The germ theory of disease is fundamental in developing medical hygiene practices.
• The  Big Bang theory is widely accepted as the leading explanation for the origin of the universe.
• The  kinetic molecular theory  explains the behavior of gases, including their volume and temperature relationships.

Related Confused Words

Hypothesis vs thesis.

A hypothesis is a specific, testable prediction that is proposed before conducting a research study, while a thesis is a statement or theory put forward to be maintained or proved. In essence, a hypothesis is a tentative assumption made in order to draw out and test its logical or empirical consequences, while a thesis is a proposition that is maintained by argument.

Both play distinct roles in the scientific and academic realms, with hypotheses guiding research and theses forming the central point of an argument or discussion.

Theory vs. Law

The primary difference between a scientific theory and a scientific law lies in their scope and function. A scientific theory is a well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and has undergone rigorous testing and validation. In contrast, a scientific law describes a concise statement or mathematical equation that summarizes a wide variety of observations and experiments, often expressing a fundamental principle of nature.

While a theory provides an overarching framework for understanding a phenomenon, a law describes a specific, observable relationship. Both theory and law are vital components of scientific understanding, with theories offering explanations and laws providing concise descriptions of natural phenomena.

• Ethics vs. Morals
• Latest Posts

• Skillset or Skill Set: Which is Correct? - March 9, 2024
• Vender or Vendor: What Is the Difference? - February 5, 2024
• Take Effect vs. Take Affect: Unraveling the Confusion - February 3, 2024

• Skip to primary navigation
• Skip to main content
• Skip to primary sidebar
• Skip to footer

Understanding Science

How science REALLY works...

Prepare and plan

Correcting misconceptions.

Many students have misconceptions about what science is and how it works. This section explains and corrects some of the most common misconceptions that students are likely have trouble with. If you are interested in common misconceptions about  teaching  the nature and process of science, visit our page on that topic .

Jump to: Misinterpretations of the scientific process | Misunderstandings of the limits of science | Misleading stereotypes of scientists | Vocabulary mix-ups | Roadblocks to learning science

Expand the individual panels to reveal the corrections or Expand all | Collapse all

Misinterpretations of the scientific process

Misconception: science is a collection of facts..

CORRECTION:

Because science classes sometimes revolve around dense textbooks, it’s easy to think that’s all there is to science: facts in a textbook. But that’s only part of the picture. Science  is  a body of knowledge that one can learn about in textbooks, but it is also a process. Science is an exciting and dynamic process for discovering how the world works and building that knowledge into powerful and coherent frameworks. To learn more about the process of science, visit our section on  How science works .

MISCONCEPTION: Science is complete.

Since much of what is taught in introductory science courses is knowledge that was constructed in the 19th and 20th centuries, it’s easy to think that science is finished — that we’ve already discovered most of what there is to know about the natural world . This is far from accurate. Science is an ongoing process, and there is much more yet to learn about the world. In fact, in science, making a key discovery often leads to many new questions ripe for investigation. Furthermore, scientists are constantly elaborating, refining, and revising established scientific ideas based on new evidence and perspectives. To learn more about this, visit our page describing how scientific ideas lead to ongoing research .

MISCONCEPTION: There is a single Scientific Method that all scientists follow.

“The Scientific Method” is often taught in science courses as a simple way to understand the basics of scientific testing. In fact, the Scientific Method represents how scientists usually write up the results of their studies (and how a few investigations are actually done), but it is a grossly oversimplified representation of how scientists generally build knowledge. The process of science is exciting, complex, and unpredictable. It involves many different people, engaged in many different activities, in many different orders. To review a more accurate representation of the process of science, explore our  flowchart .

MISCONCEPTION: The process of science is purely analytic and does not involve creativity.

Perhaps because the Scientific Method presents a linear and rigid representation of the process of science, many people think that doing science involves closely following a series of steps, with no room for creativity and inspiration. In fact, many scientists recognize that creative thinking is one of the most important skills they have — whether that creativity is used to come up with an alternative hypothesis, to devise a new way of testing an idea, or to look at old data in a new light. Creativity is critical to science!

MISCONCEPTION: When scientists analyze a problem, they must use either inductive or deductive reasoning.

Scientists use all sorts of different reasoning modes at different times — and sometimes at the same time — when analyzing a problem. They also use their creativity to come up with new ideas, explanations, and tests. This isn’t an either/or choice between induction and deduction. Scientific analysis often involves jumping back and forth among different modes of reasoning and creative brainstorming! What’s important about scientific reasoning is not what all the different modes of reasoning are called, but the fact that the process relies on careful, logical consideration of how evidence supports or does not support an idea, of how different scientific ideas are related to one another, and of what sorts of things we can expect to observe if a particular idea is true. If you are interested in learning about the difference between induction and deduction, visit our  FAQ on the topic .

MISCONCEPTION: Experiments are a necessary part of the scientific process. Without an experiment, a study is not rigorous or scientific.

Perhaps because the Scientific Method and popular portrayals of science emphasize  experiments , many people think that science can’t be done  without  an experiment. In fact, there are  many  ways to test almost any scientific idea; experimentation is only one approach. Some ideas are best tested by setting up a  controlled experiment  in a lab, some by making detailed observations of the natural world, and some with a combination of strategies. To study detailed examples of how scientific ideas can be tested fairly, with and without experiments, check out our side trip  Fair tests: A do-it-yourself guide .

MISCONCEPTION: "Hard" sciences are more rigorous and scientific than "soft" sciences.

Some scientists and philosophers have tried to draw a line between “hard” sciences (e.g., chemistry and physics) and “soft” ones (e.g., psychology and sociology). The thinking was that hard science used more rigorous, quantitative methods than soft science did and so were more trustworthy. In fact, the rigor of a scientific study has much more to do with the investigator’s approach than with the discipline. Many psychology studies, for example, are carefully controlled, rely on large sample sizes, and are highly quantitative. To learn more about how rigorous and fair tests are designed, regardless of discipline, check out our side trip  Fair tests: A do-it-yourself guide .

MISCONCEPTION: Scientific ideas are absolute and unchanging.

Because science textbooks change very little from year to year, it’s easy to imagine that scientific ideas don’t change at all. It’s true that some scientific ideas are so well established and supported by so many lines of evidence, they are unlikely to be completely overturned. However, even these established ideas are subject to modification based on new evidence and perspectives. Furthermore, at the cutting edge of scientific research — areas of knowledge that are difficult to represent in introductory textbooks — scientific ideas may change rapidly as scientists test out many different possible explanations trying to figure out which are the most accurate. To learn more about this, visit our page describing  how science aims to build knowledge .

MISCONCEPTION: Because scientific ideas are tentative and subject to change, they can't be trusted.

Especially when it comes to scientific findings about health and medicine, it can sometimes seem as though scientists are always changing their minds. One month the newspaper warns you away from chocolate’s saturated fat and sugar; the next month, chocolate companies are bragging about chocolate’s antioxidants and lack of trans-fats. There are several reasons for such apparent reversals. First, press coverage tends to draw particular attention to disagreements or ideas that conflict with past views. Second, ideas at the cutting edge of research (e.g., regarding new medical studies) may change rapidly as scientists test out many different possible explanations trying to figure out which are the most accurate. This is a normal and healthy part of the process of science. While it’s true that all scientific ideas are subject to change if warranted by the evidence, many scientific ideas (e.g., evolutionary theory, foundational ideas in chemistry) are supported by many lines of evidence, are extremely reliable, and are unlikely to change. To learn more about provisionality in science and its portrayal by the media, visit a section from our  Science Toolkit .

MISCONCEPTION: Scientists' observations directly tell them how things work (i.e., knowledge is "read off" nature, not built).

Because science relies on observation and because the process of science is unfamiliar to many, it may seem as though scientists build knowledge directly through observation. Observation  is  critical in science, but scientists often make  inferences  about what those observations mean. Observations are part of a complex process that involves coming up with ideas about how the natural world works and seeing if observations back those explanations up. Learning about the inner workings of the natural world is less like reading a book and more like writing a non-fiction book — trying out different ideas, rephrasing, running drafts by other people, and modifying text in order to present the clearest and most accurate explanations for what we observe in the natural world. To learn more about how scientific knowledge is built, visit our section  How science works .

MISCONCEPTION: Science proves ideas.

Journalists often write about “scientific proof” and some scientists talk about it, but in fact, the concept of proof — real, absolute proof — is not particularly scientific. Science is based on the principle that  any  idea, no matter how widely accepted today, could be overturned tomorrow if the evidence warranted it. Science accepts or rejects ideas based on the evidence; it does not prove or disprove them. To learn more about this, visit our page describing  how science aims to build knowledge .

MISCONCEPTION: Science can only disprove ideas.

This misconception is based on the idea of falsification, philosopher Karl Popper’s influential account of scientific justification, which suggests that all science can do is reject, or falsify, hypotheses — that science cannot find evidence that  supports  one idea over others. Falsification was a popular philosophical doctrine — especially with scientists — but it was soon recognized that falsification wasn’t a very complete or accurate picture of how scientific knowledge is built. In science, ideas can never be completely proved or completely disproved. Instead, science accepts or rejects ideas based on supporting and refuting evidence, and may revise those conclusions if warranted by new evidence or perspectives.

MISCONCEPTION: If evidence supports a hypothesis, it is upgraded to a theory. If the theory then garners even more support, it may be upgraded to a law.

This misconception may be reinforced by introductory science courses that treat hypotheses as “things we’re not sure about yet” and that only explore established and accepted theories. In fact, hypotheses, theories, and laws are rather like apples, oranges, and kumquats: one cannot grow into another, no matter how much fertilizer and water are offered. Hypotheses, theories, and laws are all scientific explanations that differ in breadth — not in level of support. Hypotheses are explanations that are limited in scope, applying to fairly narrow range of phenomena. The term  law  is sometimes used to refer to an idea about how observable phenomena are related — but the term is also used in other ways within science. Theories are deep explanations that apply to a broad range of phenomena and that may integrate many hypotheses and laws. To learn more about this, visit our page on  the different levels of explanation in science .

MISCONCEPTION: Scientific ideas are judged democratically based on popularity.

When newspapers make statements like, “most scientists agree that human activity is the culprit behind global warming,” it’s easy to imagine that scientists hold an annual caucus and vote for their favorite hypotheses. But of course, that’s not quite how it works. Scientific ideas are judged not by their popularity, but on the basis of the evidence supporting or contradicting them. A hypothesis or theory comes to be accepted by many scientists (usually over the course of several years — or decades!) once it has garnered many lines of supporting evidence and has stood up to the scrutiny of the scientific community. A hypothesis accepted by “most scientists,” may not be “liked” or have positive repercussions, but it is one that science has judged likely to be accurate based on the evidence. To learn more about  how science judges ideas , visit our series of pages on the topic in our section on how science works.

MISCONCEPTION: The job of a scientist is to find support for his or her hypotheses.

This misconception likely stems from introductory science labs, with their emphasis on getting the “right” answer and with congratulations handed out for having the “correct” hypothesis all along. In fact, science gains as much from figuring out which hypotheses are likely to be wrong as it does from figuring out which are supported by the evidence. Scientists may have personal favorite hypotheses, but they strive to consider multiple hypotheses and be unbiased when evaluating them against the evidence. A scientist who finds evidence contradicting a favorite hypothesis may be surprised and probably disappointed, but can rest easy knowing that he or she has made a valuable contribution to science.

MISCONCEPTION: Scientists are judged on the basis of how many correct hypotheses they propose (i.e., good scientists are the ones who are "right" most often).

The scientific community  does  value individuals who have good intuition and think up creative explanations that turn out to be correct — but it  also  values scientists who are able to think up creative ways to test a new idea (even if the test ends up contradicting the idea) and who spot the fatal flaw in a particular argument or test. In science, gathering evidence to determine the accuracy of an explanation is just as important as coming up with the explanation that winds up being supported by the evidence.

MISCONCEPTION: Investigations that don't reach a firm conclusion are useless and unpublishable.

Perhaps because the last step of the Scientific Method is usually “draw a conclusion,” it’s easy to imagine that studies that don’t reach a clear conclusion must not be scientific or important. In fact,  most  scientific studies don’t reach “firm” conclusions. Scientific articles usually end with a discussion of the limitations of the tests performed and the alternative hypotheses that might account for the phenomenon. That’s the nature of scientific knowledge — it’s inherently tentative and could be overturned if new evidence, new interpretations, or a better explanation come along. In science, studies that carefully analyze the strengths and weaknesses of the test performed and of the different alternative explanations are particularly valuable since they encourage others to more thoroughly scrutinize the ideas and evidence and to develop new ways to test the ideas. To learn more about publishing and scrutiny in science, visit our discussion of  peer review .

MISCONCEPTION: Scientists are completely objective in their evaluation of scientific ideas and evidence.

Scientists do strive to be unbiased as they consider different scientific ideas, but scientists are people too. They have different personal beliefs and goals — and may favor different hypotheses for different reasons. Individual scientists may not be completely objective, but science can overcome this hurdle through the action of the scientific community, which scrutinizes scientific work and helps balance biases. To learn more, visit  Scientific scrutiny  in our section on the social side of science.

MISCONCEPTION: Scientists' personal traits, experiences, emotions, and values don't factor into the process of science.

Scientists’ personal traits, experiences, emotions, and values influence their selection of research topic, hypotheses, chosen research methods, and interpretations of results and evidence, shaping the course of science in many ways. For example, a social scientist who has experienced poverty might be more likely to study this topic and might formulate different hypotheses about its causes than someone from a different background. Furthermore, experiencing curiosity and wonder is a key motivation for many scientists to pursue their work. Because science is a human endeavor, these fundamentally human traits (our unique identities, emotions, and values) play their role in the process. This means that scientists cannot be completely objective (see above). However, individual biases can be overcome through community scrutiny, helping science self-correct and continue to build more and more accurate explanations for how the world works.

MISCONCEPTION: Science is pure. Scientists work without considering the applications of their ideas.

It’s true that some scientific research is performed without any attention to its applications, but this is certainly not true of all science. Many scientists choose specific areas of research (e.g., malaria genetics) because of the practical ramifications new knowledge in these areas might have. And often, basic research that is performed without any aim toward potential applications later winds up being extremely useful. To learn about some of the many applications of scientific knowledge visit  What has science done for you lately?

Misunderstandings of the limits of science

Misconception: science contradicts the existence of god..

Because of some vocal individuals (both inside and outside of science) stridently declaring their beliefs, it’s easy to get the impression that science and religion are at war. In fact, people of many different faiths and levels of scientific expertise see no contradiction at all between science and religion. Because science deals only with  natural  phenomena and explanations, it cannot support or contradict the existence of  supernatural  entities — like God. To learn more, visit our side trip  Science and religion: Reconcilable differences .

MISCONCEPTION: Science and technology can solve all our problems.

The feats accomplished through the application of scientific knowledge are truly astounding. Science has helped us eradicate deadly diseases, communicate with people all over the world, and build  technologies  that make our lives easier everyday. But for all scientific innovations, the costs must be carefully weighed against the benefits. And, of course, there’s no guarantee that solutions for some problems (e.g., finding an HIV vaccine) exist — though science is likely to help us discover them if they do exist. Furthermore, some important human concerns (e.g. some spiritual and aesthetic questions) cannot be addressed by science at all. Science is a marvelous tool for helping us understand the natural world, but it is not a cure-all for whatever problems we encounter.

Misleading stereotypes of scientists

Misconception: science is a solitary pursuit..

When scientists are portrayed in movies and television shows, they are often ensconced in silent laboratories, alone with their bubbling test-tubes. This can make science seem isolating. In fact, many scientists work in busy labs or field stations, surrounded by other scientists and students. Scientists often collaborate on studies with one another, mentor less experienced scientists, and just chat about their work over coffee. Even the rare scientist who works entirely alone depends on interactions with the rest of the scientific community to scrutinize his or her work and get ideas for new studies. Science is a social endeavor. To learn more, visit our section on the  Social side of science .

MISCONCEPTION: Science is done by "old, white men."

While it is true that Western science used to be the domain of white males, this is no longer the case. The diversity of the scientific community is expanding rapidly. Science is open to anyone who is curious about the natural world and who wants to take a scientific approach to his or her investigations. To see how science benefits from a diverse community, visit  Diversity makes the difference .

MISCONCEPTION: Scientists are atheists.

This is far from true. A 2005 survey of scientists at top research universities found that more than 48% had a religious affiliation and that more than 75% believed that religions convey important truths. 1  Some scientists are not religious, but many others subscribe to a specific faith and/or believe in higher powers. Science itself is a secular pursuit, but welcomes participants from all religious faiths. To learn more, visit our side trip  Science and religion: Reconcilable differences .

Vocabulary mix-ups

Some misconceptions occur simply because scientific language and everyday language use some of the same words differently.

Facts  are statements that we know to be true through direct  observation . In everyday usage, facts are a highly valued form of knowledge because we can be so confident in them. Scientific thinking, however, recognizes that, though facts are important, we can only be completely confident about relatively simple statements. For example, it may be a fact that there are three trees in your backyard. However, our knowledge of how all trees are related to one another is not a fact; it is a complex body of knowledge based on many different  lines of evidence  and reasoning that may change as new  evidence  is discovered and as old evidence is interpreted in new ways. Though our knowledge of tree relationships is not a fact, it is broadly applicable, useful in many situations, and synthesizes many individual facts into a broader framework.  Science  values facts but recognizes that many forms of knowledge are more powerful than simple facts.

In everyday language, a  law  is a rule that must be abided or something that can be relied upon to occur in a particular situation. Scientific laws, on the other hand, are less rigid. They may have exceptions, and, like other scientific knowledge, may be modified or rejected based on new evidence and perspectives. In science, the term  law  usually refers to a generalization about  data  and is a compact way of describing what we’d expect to happen in a particular situation. Some laws are non-mechanistic statements about the relationship among observable phenomena. For example, the ideal gas law describes how the pressure, volume, and temperature of a particular amount of gas are related to one another. It does not describe how gases  must  behave; we know that gases do not precisely conform to the ideal gas law. Other laws deal with phenomena that are not directly observable. For example, the second law of thermodynamics deals with entropy, which is not directly observable in the same way that volume and pressure are. Still other laws offer more mechanistic explanations of phenomena. For example, Mendel’s first law offers a  model  of how genes are distributed to gametes and offspring that helps us make  predictions  about the outcomes of genetic crosses. The term  law  may be used to describe many different forms of scientific knowledge, and whether or not a particular idea is called a law has much to do with its discipline and the time period in which it was first developed.

Observation

In everyday language, the word  observation  generally means something that we’ve seen with our own eyes. In science, the term is used more broadly. Scientific observations can be made directly with our own senses or may be made indirectly through the use of tools like thermometers, pH test kits, Geiger counters, etc. We can’t actually  see  beta particles, but we can observe them using a Geiger counter. To learn more about the role of observation in science, visit  Observation beyond our eyes  in our section on how science works.

In everyday language, the word  hypothesis  usually refers to an educated guess — or an idea that we are quite uncertain about. Scientific hypotheses, however, are much more informed than any guess and are usually based on prior experience, scientific background knowledge, preliminary observations, and logic. In addition, hypotheses are often supported by many different lines of evidence — in which case, scientists are more confident in them than they would be in any mere “guess.” To further complicate matters, science textbooks frequently misuse the term in a slightly different way. They may ask students to make a  hypothesis  about the outcome of an experiment (e.g., table salt will dissolve in water more quickly than rock salt will). This is simply a prediction or a guess (even if a well-informed one) about the outcome of an experiment. Scientific hypotheses, on the other hand, have explanatory power — they are explanations for phenomena. The idea that table salt dissolves faster than rock salt is not very hypothesis-like because it is not very explanatory. A more scientific (i.e., more explanatory) hypothesis might be “The amount of surface area a substance has affects how quickly it can dissolve. More surface area means a faster rate of dissolution.” This hypothesis has some explanatory power — it gives us an idea of  why  a particular phenomenon occurs — and it is testable because it generates expectations about what we should observe in different situations. If the hypothesis is accurate, then we’d expect that, for example, sugar processed to a powder should dissolve more quickly than granular sugar. Students could examine rates of dissolution of many different substances in powdered, granular, and pellet form to further test the idea. The statement “Table salt will dissolve in water more quickly than rock salt” is not a hypothesis, but an expectation generated by a hypothesis. Textbooks and science labs can lead to confusions about the difference between a hypothesis and an expectation regarding the outcome of a scientific test. To learn more about scientific hypotheses, visit  Science at multiple levels  in our section on how science works.

In everyday language, the word  theory  is often used to mean a hunch with little evidential support. Scientific theories, on the other hand, are broad explanations for a wide range of phenomena. They are concise (i.e., generally don’t have a long list of exceptions and special rules), coherent, systematic, and can be used to make predictions about many different sorts of situations. A theory is most  acceptable  to the scientific community when it is strongly supported by many different lines of evidence — but even theories may be modified or overturned if warranted by new evidence and perspectives. To learn more about scientific theories, visit  Science at multiple levels  in our section on how science works.

Falsifiable

The word  falsifiable  isn’t used much in everyday language, but when it is, it is often applied to ideas that have been shown to be untrue. When that’s the case — when an idea has been shown to be false — a scientist would say that it has been falsified. A falsifi able  idea, on the other hand, is one for which there is a conceivable  test  that might produce evidence proving the idea false. Scientists and others influenced by the ideas of the philosopher Karl Popper sometimes assert that only falsifiable ideas are scientific. However, we now recognize that science cannot once-and-for-all prove any idea to be false (or true for that matter). Furthermore, it’s clear that evidence can play a role in supporting particular ideas over others — not just in ruling some ideas out, as implied by the falsifiability criterion. When a scientist says  falsifiable , he or she probably actually means something like  testable , the term we use in this website to avoid confusion. A testable idea is one about which we could gather evidence to help determine whether or not the idea is accurate.

Uncertainty

In everyday language,  uncertainty  suggests the state of being unsure of something. Scientists, however, usually use the word when referring to measurements. The uncertainty of a measurement (not to be confused with the inherent provisionality of all scientific ideas!) is the range of values within which the true value is likely to fall. In science, uncertainty is not a bad thing; it’s simply a fact of life. Every measurement has some uncertainty. If you measure the length of a pen with a standard ruler, you won’t be able to tell whether its length is 5.880 inches, 5.875 inches, or 5.870 inches. A ruler with more precision will help narrow that range, but cannot eliminate uncertainty entirely. For more on a related idea, see our discussion of  error  below.

In everyday language, an error is simply a mistake, but in science, error has a precise statistical meaning. An error is the difference between a measurement and the true value, often resulting from taking a  sample . For example, imagine that you want to know if corn plants produce more massive ears when grown with a new fertilizer, and so you weigh ears of corn from those plants. You take the mass of your sample of 50 ears of corn and calculate an average. That average is a good estimate of what you are really interested in: the average mass of  all  ears of corn that could be grown with this fertilizer. Your estimate is not a mistake — but it does have an error (in the statistical sense of the word) since your estimate is not the true value. Sampling error of the sort described above is inherent whenever a smaller sample is taken to represent a larger entity. Another sort of error results from systematic biases in measurement (e.g., if your scale were calibrated improperly, all of your measurements would be off). Systematic error biases measurements in a particular direction and can be more difficult to quantify than sampling error.

In everyday language,  prediction  generally refers to something that a fortune teller makes about the future. In science, the term  prediction  generally means “what we would expect to happen or what we would expect to observe if this idea were accurate.” Sometimes, these scientific predictions have nothing at all to do with the future. For example, scientists have hypothesized that a huge asteroid struck the Earth 4.5 billion years ago, flinging off debris that formed the moon. If this idea were true, we would  predict  that the moon today would have a similar composition to that of the Earth’s crust 4.5 billion years ago — a prediction which does seem to be accurate. This hypothesis deals with the deep history of our solar system and yet it involves predictions — in the scientific sense of the word. Ironically, scientific predictions often have to do with past events. In this website, we’ve tried to reduce confusion by using the words  expect and  expectation  instead of  predict  and  prediction . To learn more, visit  Predicting the past  in our section on the core of science.

Belief/believe

When we, in everyday language, say that we believe in something, we may mean many things — that we support a cause, that we have faith in an idea, or that we think something is accurate. The word  belief  is often associated with ideas about which we have strong convictions, regardless of the evidence for or against them. This can generate confusion when a scientist claims to “believe in” a scientific hypothesis or theory. In fact, the scientist probably means that he or she “ accepts ” the idea — in other words, that he or she thinks the scientific idea is the most accurate available based on a critical evaluation of the evidence. Scientific ideas should always be accepted or rejected based on the evidence for or against them — not based on faith, dogma, or personal conviction.

Roadblocks to learning science

In school, many students get the wrong impression of science. While not technically misconceptions, these overgeneralizations are almost always inaccurate — and can make it more difficult for the students who hold them to learn science.

MISCONCEPTION: Science is boring.

  Memorizing facts from a textbook can be boring — but science is much more than the knowledge that makes its way into school books. Science is an ongoing and unfinished process of discovery. Some scientists travel all over the world for their research. Others set up experiments that no one has ever tried before. And all scientists are engaged in a thrilling quest — to learn something brand new about the natural world. Some parts of scientific training or investigations may be tedious, but science itself is exciting! To see how a scientific perspective can make the world a more exciting and intriguing place, visit our side trip  Think science .

MISCONCEPTION: Science isn't important in my life.

It’s easy to think that what scientists do in far-off laboratories and field stations has little relevance to your everyday life — after all, not many of us deal with super colliders or arctic plankton on a regular basis — but take another look around you. All the technologies, medical advances, and knowledge that improve our lives everyday are partly the result of scientific research. Furthermore, the choices you make when you vote in elections and support particular causes can influence the course of science. Science is deeply interwoven with our everyday lives. To see how society influences science, visit  Science and society . To learn more about how scientific advances affect your life, visit  What has science done for you lately?

MISCONCEPTION: I am not good at science.

Some students find science class difficult — but this doesn’t translate to not being good at science. First of all, school science can be very different from real science. The background knowledge that one learns in school is important for practicing scientists, but it is only part of the picture. Scientific research also involves creative problem-solving, communicating with others, logical reasoning, and many other skills that might or might not be a part of every science class. Second, science encompasses a remarkably broad set of activities. So maybe you don’t care much for the periodic table — but that doesn’t mean that you wouldn’t be great at observing wild chimpanzee behavior, building computer models of tectonic plate movement, or giving talks about psychology experiments at scientific meetings. Often when a student claims to “not be good at science,” it really just means that he or she hasn’t yet found a part of science that clicks with his or her interests and talents.

1 Ecklund, E.H., and C.P. Scheitle. 2007. Religion among academic scientists: Distinctions, disciplines, and demographics.  Social Problems  54(2):289-307.

• Teaching resources
• Unfortunately, many textbooks promulgate misconceptions about the nature and process of science. Use this list to review your textbook, and then discuss any misrepresentations with students.
• You can highlight misconceptions about science that are promulgated in the media by starting a bulletin board that highlights examples of misconceptions found in the popular press — for example, misuses of the word theory, implications that scientists always use “the scientific method,” or that experimental science is more rigorous than non-experimental science.
• Use word lists to combat misconceptions about science that stem from vocabulary mix-ups. Find out how in this article distributed with permission from Science Scope.

Alignment with science standards

Educational research

Subscribe to our newsletter

• Understanding Science 101
• The science flowchart
• Science stories
• Grade-level teaching guides
• Teaching resource database
• Journaling tool
• Misconceptions

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Published: 22 August 2024

Conceptual structure and the growth of scientific knowledge

• Kara Kedrick   ORCID: orcid.org/0000-0002-3410-5834 1 ,
• Ekaterina Levitskaya 2 &
• Russell J. Funk   ORCID: orcid.org/0000-0001-6670-4981 3  

Nature Human Behaviour ( 2024 ) Cite this article

853 Accesses

12 Altmetric

Metrics details

• Computer science
• Science, technology and society

How does scientific knowledge grow? This question has occupied a central place in the philosophy of science, stimulating heated debates but yielding no clear consensus. Many explanations can be understood in terms of whether and how they view the expansion of knowledge as proceeding through the accretion of scientific concepts into larger conceptual structures. Here we examine these views empirically by analysing 2,605,224 papers spanning five decades from both the social sciences (Web of Science) and the physical sciences (American Physical Society). Using natural language processing techniques, we create semantic networks of concepts, wherein noun phrases become linked when used in the same paper abstract. We then detect the core/periphery structures of these networks, wherein core concepts are densely connected sets of highly central nodes and periphery concepts are sparsely connected nodes that are highly connected to the core. For both the social and physical sciences, we observe increasingly rigid conceptual cores accompanied by the proliferation of periphery concepts. Subsequently, we examine the relationship between conceptual structure and the growth of scientific knowledge, finding that scientific works are more innovative in fields with cores that have higher conceptual churn and with larger cores. Furthermore, scientific consensus is associated with reduced conceptual churn and fewer conceptual cores. Overall, our findings suggest that while the organization of scientific concepts is important for the growth of knowledge, the mechanisms vary across time.

This is a preview of subscription content, access via your institution

Access options

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

24,99 € / 30 days

cancel any time

Subscribe to this journal

Receive 12 digital issues and online access to articles

111,21 € per year

only 9,27 € per issue

Buy this article

• Purchase on SpringerLink
• Instant access to full article PDF

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

Papers and patents are becoming less disruptive over time

Leading countries in global science increasingly receive more citations than other countries doing similar research

Surprising combinations of research contents and contexts are related to impact and emerge with scientific outsiders from distant disciplines

Data availability.

The WoS data and the APS data are available from the Web of Science and the American Physical Society, respectively, but restrictions apply to the availability of these data, which were used under licence for the current study and so are not publicly available. If you are interested in accessing the WoS data, you can request access to the API through Clarivate, which requires an additional subscription or permission ( https://clarivate.com/products/scientific-and-academic-research/research-discovery-and-workflow-solutions/webofscience-platform/web-of-science-core-collection/ ). For access to the APS data, you can request permission directly from their website ( https://journals.aps.org/datasets/ ).

Code availability

The Python v.3 and Stata v.18 code we used to analyse and visualize the data for the current study are publicly available via Zenodo at https://doi.org/10.5281/zenodo.11533199 (ref. 49 ).

Price, D. J. d. S. Science since Babylon (Yale Univ. Press, 1961).

Price, D. J. d. S. Little Science, Big Science (Columbia Univ. Press, 1963).

Bornmann, L., Devarakonda, S., Tekles, A. & Chacko, G. Are disruption index indicators convergently valid? The comparison of several indicator variants with assessments by peers. Quant. Sci. Stud. 1 , 1242–1259 (2020).

Article   Google Scholar  

Milojević, S. Quantifying the cognitive extent of science. J. Informetr. 9 , 962–973 (2015).

Tabah, A. N. Literature dynamics: studies on growth, diffusion, and epidemics. Annu. Rev. Inf. Sci. Technol. 34 , 249–286 (1999).

Google Scholar  

Kuhn, T. S. The Structure of Scientific Revolutions (Univ. Chicago Press, 1962).

Lakatos, I. & Musgrave, A. Criticism and the Growth of Knowledge: Proceedings of the International Colloquium in the Philosophy of Science, London, 1965 Vol. 4 (Cambridge Univ. Press, 1970).

Laudan, L. Progress and Its Problems: Toward a Theory of Scientific Growth (Univ. California Press, 1978).

Popper, K. R. Conjectures and Refutations: The Growth of Scientific Knowledge (Routledge & Kegan Paul, 2002).

Cole, S. Why sociology doesn’t make progress like the natural sciences. Sociol. Forum 9 , 133–154 (1994).

Cole, S. Disciplinary knowledge revisited: the social construction of sociology. Am. Sociol. 37 , 41–56 (2006).

Gonzalez, W. J. Prediction and Novel Facts in the Methodology of Scientific Research Programs 103–124 (Springer International, 2015).

Chu, J. S. G. & Evans, J. A. Slowed canonical progress in large fields of science. Proc. Natl Acad. Sci. USA 118 , e2021636118 (2021).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Newman, M. E. J. Scientific collaboration networks. ii. Shortest paths, weighted networks, and centrality. Phys. Rev. E 64 , 016132 (2001).

Article   CAS   Google Scholar  

Latour, B. Science in Action: How to Follow Scientists and Engineers through Society (Harvard Univ. Press, 1987).

Lakatos, I., Worrall, J., Currie, G. & Currie, P. The Methodology of Scientific Research Programmes: Philosophical Papers Vol. 1 (Cambridge Univ. Press, 1978).

Kojaku, S. & Masuda, N. Finding multiple core–periphery pairs in networks. Phys. Rev. E 96 , 052313 (2017).

Article   PubMed   Google Scholar  

Borgatti, S. P. & Everett, M. G. Models of core/periphery structures. Soc. Netw. 21 , 375–395 (2000).

Funk, R. J. & Owen-Smith, J. A dynamic network measure of technological change. Manage. Sci. 63 , 791–817 (2017).

Mulkay, M. J., Gilbert, G. N. & Woolgar, S. Problem areas and research networks in science. Sociology 9 , 187–203 (1975).

Wimsatt, W. C. Reductionism and its heuristics: making methodological reductionism honest. Synthese 151 , 445–475 (2006).

Wu, L., Wang, D. & Evans, J. A. Large teams develop and small teams disrupt science and technology. Nature 566 , 378–382 (2019).

Article   CAS   PubMed   Google Scholar  

Shwed, U. & Bearman, P. S. The temporal structure of scientific consensus formation. Am. Sociol. Rev. 75 , 817–840 (2010).

Article   PubMed   PubMed Central   Google Scholar  

Mayo, L. C., McCue, S. W. & Moroney, T. J. Gravity-driven fingering simulations for a thin liquid film flowing down the outside of a vertical cylinder. Phys. Rev. E 87 , 053018 (2013).

Jones, B. F. The burden of knowledge and the ‘death of the Renaissance Man’: is innovation getting harder? Rev. Econ. Stud. 76 , 283–317 (2009).

Gordon, R. J. The Rise and Fall of American Growth: The U.S. Standard of Living since the Civil War revised edn (Princeton Univ. Press, 2016).

Bhattacharya, J. & Packalen, M. Stagnation and Scientific Incentives Working Paper No. 26752 (National Bureau of Economic Research, 2020).

Fink, T., Reeves, M., Palma, R. & Farr, R. S. Serendipity and strategy in rapid innovation. Nat. Commun. 8 , 2002 (2017).

Tria, F., Loreto, V., Servedio, V. & Strogatz, S. The dynamics of correlated novelties. Sci. Rep. 4 , 5890 (2014).

Bloom, N., Jones, C. I., Van Reenen, J. & Webb, M. Are ideas getting harder to find? Am. Econ. Rev. 110 , 1104–1144 (2020).

Horgan, J. The End of Science: Facing the Limits of Knowledge in the Twilight of the Scientific Age (Basic Books, 2015).

Jones, B. F. & Weinberg, B. A. Age dynamics in scientific creativity. Proc. Natl Acad. Sci. USA 108 , 18910–18914 (2011).

Duncker, K. On problem solving. Psychol. Monogr . 58 , i–113 (1945).

Jansson, D. G. & Smith, S. M. Design fixation. Des. Stud. 12 , 3–11 (1991).

Maier, N. R. F. Reasoning in humans: II. The solution of a problem and its appearance in consciousness. J. Compar. Psychol. 12 , 181–194 (1931).

Smith, S. M., Ward, T. B. & Schumacher, J. S. Constraining effects of examples in a creative generation task. Mem. Cogn. 21 , 837–845 (1993).

Cole, S. Making Science: Between Nature and Society (Harvard Univ. Press, 1995).

Van Rossum, G. & Drake, F. L. Python 3 Reference Manual. (CreateSpace, 2009).

MariaDB Foundation. MariaDB. https://mariadb.com/ (2023).

Mongeon, P. & Paul-Hus, A. The journal coverage of Web of Science and Scopus: a comparative analysis. Scientometrics 106 , 213–228 (2016).

Tennant, J. P. Web of Science and Scopus are not global databases of knowledge. Eur. Sci. Ed. 46 , e51987 (2020).

Christianson, N. H., Sizemore Blevins, A. & Bassett, D. S. Architecture and evolution of semantic networks in mathematics texts. Proc. R. Soc. A 476 , 20190741 (2020).

Dworkin, J. D., Shinohara, R. T. & Bassett, D. S. The emergent integrated network structure of scientific research. PLoS ONE 14 , e0216146 (2019).

Rule, A., Cointet, J.-P. & Bearman, P. S. Lexical shifts, substantive changes, and continuity in State of the Union discourse, 1790–2014. Proc. Natl Acad. Sci. USA 112 , 10837–10844 (2015).

Honnibal, M., Montani, I., Van Landeghem, S. & Boyd, A. spaCy: industrial-strength natural language processing in Python. Zenodo https://zenodo.org/records/10009823 (2020).

DeWilde, B. textacy documentation (Chartbeat, Inc., 2021).

Hofstra, B. et al. The diversity–innovation paradox in science. Proc. Natl Acad. Sci. USA 117 , 9284–9291 (2020).

Kojaku, S. & Masuda, N. Core–periphery structure requires something else in the network. New J. Phys. 20 , 043012 (2018).

Kedrick, K., Levitskaya, E. & Funk, R. J. Conceptual structure and the growth of scientific knowledge. Zenodo https://doi.org/10.5281/zenodo.11533199 (2024).

Davis, R. L. Quantum turbulence. Phys. Rev. Lett. 64 , 2519–2522 (1990).

Download references

Acknowledgements

We thank the National Science Foundation for financial support of work related to this project (grants no. 1829168 to R.J.F and no. 1932596 to R.J.F). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. We also thank D. Hirschman, M. Park and Y. J. Kim for feedback on an earlier version of this work, and T. Gebhart for many helpful conversations and assistance with data and computation. Our work was presented as a poster at the 2nd Annual International Conference on the Science of Science and Innovation, as a poster at the 43rd Annual Meeting of the Cognitive Science Society, as a lightning talk at Networks 2021: A Joint Sunbelt and NetSci Conference, and as a poster at the 3rd North American Social Networks Conference.

Author information

Authors and affiliations.

Institute for Complex Social Dynamics, Carnegie Mellon University, Pittsburgh, PA, USA

Kara Kedrick

The Coleridge Initiative, New York, NY, USA

Ekaterina Levitskaya

Carlson School of Management, University of Minnesota, Minneapolis, MN, USA

Russell J. Funk

You can also search for this author in PubMed   Google Scholar

Contributions

The study was conceptualized and designed by K.K., E.L. and R.J.F. The data analysis was conducted by K.K. and R.J.F. The manuscript was initially drafted by K.K., E.L. and R.J.F., with subsequent revisions made by K.K. and R.J.F.

Corresponding author

Correspondence to Russell J. Funk .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Peer review

Peer review information.

Nature Human Behaviour thanks Sadamori Kojaku, Marc Santolini and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended data fig. 1 concepts extracted from the text of an abstract..

This figure shows an example abstract from the APS data; the highlighted text indicates single-word and multi-word noun phrases identified as concepts using our extraction algorithm. Reproduced with permission from ref. 50 , American Physical Society.

Supplementary information

Supplementary information.

Supplementary Figs. 1–9 and Tables 1–3.

Reporting Summary

Rights and permissions.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Cite this article.

Kedrick, K., Levitskaya, E. & Funk, R.J. Conceptual structure and the growth of scientific knowledge. Nat Hum Behav (2024). https://doi.org/10.1038/s41562-024-01957-x

Download citation

Received : 29 September 2022

Accepted : 16 July 2024

Published : 22 August 2024

DOI : https://doi.org/10.1038/s41562-024-01957-x

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing: AI and Robotics newsletter — what matters in AI and robotics research, free to your inbox weekly.

Advertisement

Stoned Ape Theory: Magic Mushrooms and Human Evolution

• Share Content on Facebook
• Share Content on LinkedIn
• Share Content on Flipboard
• Share Content on Reddit
• Share Content via Email

Psychedelic research has experienced a renaissance in recent years, but as the scientific community reconsiders psilocybin's potential to treat addiction and psychiatric disturbance , where does that leave the stoned ape theory ? Did psychedelics stimulate human consciousness?

First proposed by 20th century ethnobotanist Terence McKenna (1946-2000) in his 1992 book " Food of the Gods ," the basic concept is that the consumption of psychedelic fungi may have played a crucial role in the development of human mind and culture.

According to the author's younger brother Dennis McKenna, the idea emerged out of conversations between the two. Dennis is himself an ethnopharmacologist and research pharmacognosist, as well as founder of the McKenna Academy of Natural Philosophy .

Misrepresentation of the Stoned Ape Theory

A 40,000-year-old 'creative explosion', back to the pleistocene, the magic enhancement of adaptive qualities, the debatable nature of conciousness.

"For a while I had the idea to write a book that would have been called 'Hallucinogens and Evolution,' but never got around to it," Dennis says via email. "While Terence's approach is different from what I would have written, there are complementarities. Terence's ideas were certainly fertilized by those conversations."

Neither Terence nor Dennis referred to this hypothesis by the name "stoned ape," which Dennis believes misrepresents the idea and dumbs down the concept. In essence, the hypothesis suggests we owe the emergence of language, self-reflection and other unique functions of the human brain to ancient ancestors who ate psilocybin mushrooms.

The exact timeline for the emergence of consciousness varies, but Dennis believes the process may have begun as far back as 2 million years ago.

"We know the brain tripled in size about 2 million years ago, and probably the ecosystems which put hominids, cattle and mushrooms together were around that old," Dennis says, referring to the dung from which psilocybin mushrooms emerge.

According to Dr. Thomas Falk, a professor of Philosophy and Education at the University of Dayton, the hypothesis also provides an explanation for the so-called "creative explosion" that occurred 40,000 years ago in homo sapiens , prior to their migration from Africa to Europe.

It is here that we see an apparent leap in cognitive ability for early humans.

"For the first time ever, these humans lived in worlds of their own creation, materially and symbolically," Falk says via email. "Like you and I, these humans were capable of creating worlds in their heads and then re-creating those worlds in the external physical and social environments. Although other homo species may have efficiently exploited nature, they remained its passive subjects. The key to this major distinction between homo sapiens sapiens and all other hominids appears to be language ."

Falk, whose areas of study include phenomenology and anthropology, says that while we have no shortage of good evidence and theory regarding the course of human evolution , the leap to self-consciousness remains a mystery.

"The stoned ape hypothesis offers a possible keystone that appears to fit together with much of the existing scientific evidence and theory," he says, though he stresses that this is only one possible answer.

In "Food of the Gods," Terence McKenna made his argument based on noted qualities of the psychedelic experience (such as augmented empathy and sensory perception), shamanistic traditions in ancient cultures, and the known and hypothetical range of psychedelic plants and fungi in ancient times.

The journey takes us back to the Pleistocene epoch, stretching between 2.6 million and 11,700 years ago, which saw major changes in climate . The changes would have put our ancestors on the move through new, challenging and bountiful environments.

"This would likely have entailed major experimentation," Falk explains, "much of which would have been harmful, and some of which would have been mutagenic, leading to epigenetic changes. This does not mean that new foods would have altered the hominid genome, but rather that they would have affected the expression of genes that were already present, thus changing our ancestors physiologically, neurochemically and culturally."

Thus, Terence presented an interpretation in which our ancestors would have followed herds of cows and other herbivores, depending on them for food and clothing, but also harvesting fungus from their dung (where psilocybin mushrooms commonly grow).

The regular consumption of these psychedelic mushrooms could have proven advantageous as early humans spread out into new territory.

"Psychedelic mushrooms appear advantageous for adaptation to new circumstances because they de-pattern the mind/brain, alter modes of perception and induce synaesthesia," Falk says. "Terence McKenna and mycologist Paul Stamets argue that these mushrooms may have allowed our ancestors to forge connections between sounds, symbols and meanings, which is the essence of 'the creative explosion': human language, symbol manipulation and communication."

Terence also argued that psilocybin would have increased visual acuity at low doses, increased sex drive and enhanced cooperation — all factors that could have proven adaptive to our ancestors.

Stamets, a vocal supporter of the theory, has also pointed out the leadership qualities that would have resulted from the mix of bravery and empathy brought on by these substances.

Written during what is sometimes described as the dark age of psychedelic research, "Food of the Gods" argued that the criminalization of psychedelic substances and lack of research into their powers paradoxically cut human beings off from an important aspect of their ascendency.

Terence was no stranger to wild personal anecdotes of psychedelic experience, and even wilder contemplations on the nature of reality. Yet while the book is full of the author's signature wit and vision, it is also, in the words of science writer John Horgan , a serious work that presents a rigorous argument.

"Rereading it after nearly 30 years, I remain impressed by how thoughtful it is," Dennis says, who wrote a new foreword for the book. "It's not heavily referenced but the key references are there. I think it was a credible piece of scholarship. The very idea invites derision and ridicule, and there was plenty of that by reviewers and others. But I think much of it betrays that many who criticized it never actually read it, or read it only superficially. Thirty years later, the idea has more support than ever based on what has been learned since."

In his 2018 book " How to Change Your Mind ," Michael Pollan called Terence McKenna's 1992 book "the epitome of all mycocentric speculation," stressing that its very premise is not susceptible to proof or disproof.

The stoned ape theory is simply not the sort of hypothesis that can be taken up by a scientific study. It involves the emergence and nature of consciousness, as well as the true potential of psychedelic compounds — all subjects rife with their own mysteries.

However, it's not the only possible explanation on the table.

"Human intelligence/consciousness appears to have been an emergent phenomenon," Falk says. "That is, there were many evolutionary factors, likely unrelated, that nevertheless entered into random combination and in so doing created a whole that was greater than the sum of its parts."

Changes in environment forced societal changes to ensure survival, and these societal changes demanded upgrades in mental capacity. Fire mastery and the emergence of cooking technology improved nutrition and made room for greater cultural and societal advancement.

Dennis, however, stresses that the stoned ape hypothesis is not meant to stand as the lone factor in human evolution.

"Obviously there were multiple factors involved," he says. "It's simplistic just to postulate that people ate mushrooms, so they were better equipped. There were many factors that influenced evolution."

The stoned ape theory gained little traction in academic circles, but it became a staple of psychedelic culture. Among its most notable advocates is mycologist Paul Stamets, who along with Dennis, points to scientific advancements in fields such as epigenetic inheritance and neuroplasticity that may further explain the mechanisms involved in psychedelics-assisted cognitive advancement.

The stoned ape theory is not likely to leap to the level of scientific theory in the foreseeable future, but the sort of modern psychedelic reconnection that Terence McKenna and others advocated might well come to pass — especially as more studies examine potential therapeutic uses. Dennis says:

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.

Around 200 species of Psilocybe mushrooms are found around the world and may be represented in the art of ancient humans. The psychotropic tryptamines psilocybin and psilocin are responsible for the altered states of awareness that we refer to as the psychedelic experience.

Please copy/paste the following text to properly cite this HowStuffWorks.com article: