Theory (Scientific vs layman’s definition)

This post is not going to get into the specific controversy I have in mind; it will lay the groundwork, stating the differences between how a science theory is defined vs a layman’s concept of a theory. In laying this groundwork I hope to set the stage for further discussions on various topics. While the most common argument where this definition should be fairly obvious to most people, I am not intending for this post to be the launching point for this discussion, that is for another day (after much more research on my part, to get the topic started off on the right foot).

A theory as defined by Websters is:

1: the analysis of a set of facts in their relation to one another
2: abstract thought : speculation
3: the general or abstract principles of a body of fact, a science, or an art
4 a: a belief, policy, or procedure proposed or followed as the basis of action
b: an ideal or hypothetical set of facts, principles, or circumstances
5: a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena
6 a: a hypothesis assumed for the sake of argument or investigation
b: an unproved assumption : conjecture
c: a body of theorems presenting a concise systematic view of a subject
synonyms see hypothesis

Of these definitions, the typical layman’s concept of a theory is closest to #2 (speculation) or #6b (an unproved assumption or conjecture).

Admittedly it is not always 100% reliable, but Wikipedia’s definition of theory states (at least it says so for today, who knows when somebody will change the entry to suit their own needs):

In common usage, the word theory is often used to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. This usage of theory leads to the common incorrect statement “It’s not a fact, it’s only a theory.” True descriptions of reality are more reflectively understood as statements which would be true independently of what people think about them. In this usage, the word is synonymous with hypothesis.

For many people all concepts and ideas can be divided into facts and theories. Under this world view, facts are 100% proven to be true. Two facts can not exclude each other since each one must be true under all circumstances. For this same group of people a theory is essentially the same as a guess. All theories are equally as valid as other theories and have essentially an equal chance of being true or false.

So, I think we have a good understanding of the typically understood layman’s definition of theory: “a conjecture, an opinion, or a speculation. But what of the Scientific understanding on a theory?

From the Webster’s definition, the concept of a scientific theory is, at least partially, #1 (the analysis of a set of facts in their relation to one another), #5 (a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena), and #6c (a body of theorems presenting a concise systematic view of a subject).

However much more accurate definitions of the scientific definition of a theory can be found at

1. a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein’s theory of relativity.
2. a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.
3. Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.
4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.
5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.
6. A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.
7. The branch of a science or art consisting of its explanatory statements, accepted principles, and methods of analysis, as opposed to practice: a fine musician who had never studied theory.
8. A set of theorems that constitute a systematic view of a branch of mathematics.
9. a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; “theories can incorporate facts and laws and tested hypotheses”; “true in fact and theory”
10. a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; “a scientific hypothesis that survives experimental testing becomes a scientific theory”
11. A systematically organized body of knowledge applicable in a relatively wide variety of circumstances, especially a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict, or otherwise explain the nature or behavior of a specified set of phenomena.
12. the general or abstract principles of a body of fact, a science, or an art
13. a plausible or scientifically acceptable general principle or body of principles offered to explain natural phenomena
14. a working hypothesis that is considered probable based on experimental evidence or factual or conceptual analysis and is accepted as a basis for experimentation
Synonyms : Theory, hypothesis are used in non-technical contexts to mean an untested idea or opinion. A theory in technical use is a more or less verified or established explanation accounting for known facts or phenomena: the theory of relativity. A hypothesis is a conjecture put forth as a possible explanation of phenomena or relations, which serves as a basis of argument or experimentation to reach the truth: This idea is only a hypothesis.

And again, to quote Wikipedia:

In science, a theory is a mathematical or logical explanation, or a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise falsified through empirical observation. It follows from this that for scientists “theory” and “fact” do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behavior are Newton’s theory of universal gravitation (see also gravitation), and general relativity.

The defining characteristic of a scientific theory is that it makes falsifiable or testable predictions about things not yet observed. The relevance, and specificity of those predictions determine how (potentially) useful the theory is. A would-be theory which makes no predictions which can be observed is not a useful theory. Predictions which are not sufficiently specific to be tested are similarly not useful. In both cases, the term ‘theory’ is inapplicable.

In practice a body of descriptions of knowledge is usually only called a theory once it has a minimum empirical basis. That is, it:

  • is consistent with pre-existing theory to the extent that the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense, and
  • is supported by many strands of evidence rather than a single foundation, ensuring that it is probably a good approximation, if not totally correct.

Additionally, a theory is generally only taken seriously if it:

  • is tentative, correctable and dynamic, in allowing for changes to be made as new data is discovered, rather than asserting certainty, and
  • is the most parsimonious explanation, sparing in proposed entities or explanations, commonly referred to as passing the Occam’s razor test.

This is true of such established theories as special and general relativity, quantum mechanics, plate tectonics, evolution, etc. Theories considered scientific meet at least most, but ideally all, of these extra criteria.

Theories do not have to be perfectly accurate to be scientifically useful. The predictions made by Classical mechanics are known to be inaccurate, but they are sufficiently good approximations in most circumstances that they are still very useful and widely used in place of more accurate but mathematically difficult theories.

Karl Popper described the characteristics of a scientific theory as follows:

  1. It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations.
  2. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory — an event which would have refuted the theory.
  3. Every “good” scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
  4. A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.
  5. Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.
  6. Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of “corroborating evidence.”)
  7. Some genuinely testable theories, when found to be false, are still upheld by their admirers — for example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later describe such a rescuing operation as a “conventionalist twist” or a “conventionalist stratagem”).

One can sum up all this by saying that according to Popper, the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.

According to Philip Kitcher, good scientific theories must have three features:

  1. Unity: “A science should be unified …. Good theories consist of just one problem-solving strategy, or a small family of problem-solving strategies, that can be applied to a wide range of problems” (1982: 47).
  2. Fecundity: “A great scientific theory, like Newton’s, opens up new areas of research. …. Because a theory presents a new way of looking at the world, it can lead us to ask new questions, and so to embark on new and fruitful lines of inquiry …. Typically, a flourishing science is incomplete. At any time, it raised more questions than it can currently answer. But incompleteness is now vice. On the contrary, incompleteness is the mother of fecundity …. A good theory should be productive; it should raise new questions and presume that those questions can be answered without giving up its problem-solving strategies” (1982: 47-48).
  3. Auxiliary hypotheses that are independently testable: “An auxiliary hypothesis ought to be testable independently of the particular problem it is introduced to solve, independently of the theory it is designed to save” (1982: 46) (e.g. the evidence for the existence of Neptune is independent of the anomalies in Uranus’s orbit).

Like other definitions of theories, including Popper’s, Kitcher makes it clear that a good theory includes statements that have (in his terms) “observational consequences.”

As we can see from these definitions, when one refers to a scientific theory, the typical layman’s concept of that word is not just different, but diametrically opposed to it. In the layman’s terms a theory is the opposite of a fact with nothing to differentiate it from other theories. In scientific terms there really are no “facts”, there are only theories with various degrees of probability, but once evidence comes to light to disprove a theory it is rejected in favor of a new theory which takes the new data into account.

Again, we can refer to the Wikipedia entry, which states:

In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it can in everyday speech. A theory is a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena. It originates from or is supported by experimental evidence (see scientific method). In this sense, a theory is a systematic and formalized expression of all previous observations, and is predictive, logical, and testable. In principle, scientific theories are always tentative, and subject to corrections or inclusion in a yet wider theory. Commonly, a large number of more specific hypotheses may be logically bound together by just one or two theories. As a general rule for use of the term, theories tend to deal with much broader sets of universals than do hypotheses, which ordinarily deal with much more specific sets of phenomena or specific applications of a theory.

It is commonly misunderstood that there are known truths that are superior to theories. If this is actually the case, then the seemingly “known truth” is actually a theory itself. One theory may be superior to another in terms of its approximation of truth, but both statements are theories. Scientific tests of the quality of a theory include its conformity to known facts and its ability to generate hypotheses with outcomes that would predict further testable facts.

A misunderstanding of the word “fact” contributes to confusion in regard to the meaning of “theory.” An appreciation of the actual meaning of “fact” and “knowledge” can help to clarify an understanding of the meaning of “theory.”

To bring this post to a conclusion, since it seems to have gotten a bit longer than I had planned, A Brief History of Time by Stephen Hawking states:

A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model which contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.

Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation which disagrees with the predictions of the theory.

So based on Hawkins, Popper, and Kitcher’s comments, we can conclude that the longer a theory has been around, and the more thoroughly it has been tested, the more we can assume that either the theory in question is correct, or is close enough to the actual “truth” of the subject to be a valuable tool in understanding the nature of that subject. And finally that a scientific theory must make predictions that can be empirically tested and is falsifiable.

While there is no one way to define a theory since it is based on context, a layman’s view of a theory (a detective may stake out a house on the theory that criminals usually return to the scene of the crime) vs a scientific theory (Einstein’s theory of general relativity, Newton’s theory of universal gravitation, Darwin’s Theory Of Evolution, etc…); we must endeavor to keep in mind the subject matter and context of the discussion when we come across the word “theory” and treat it thusly.

About Rodibidably

Jeff Randall is a frequent volunteer for free-thought organizations, including the Center For Inquiry – DC. Having been blogging since January 2008, he decided that a community of bloggers would be an interesting new experience (or at the very least a fun way to annoy his friends into reading his posts more frequently). Since finding out about about the existence of, and then joining, the atheist/skeptic community in 2007 he has been committed to community activism, critical thinking in all aspects of life, science, reason, and a fostering a secular society.
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22 Responses to Theory (Scientific vs layman’s definition)

  1. Pingback: Theory (Scientific vs layman’s definition) | Rodibidably

  2. Jeff Randall says:

    An interesting point was brought up on FB regarding this post, and I thought it was worth sharing.

    A friend of mine who works for a large national science organization said:

    Interesting piece. For the layman, I think it helps to reinforce that ‘theory’ is like an explanation, whereas ‘law’ is just an observation. Moving beyond that to the discussion of the systematic framework may be a bit much without any background. There is some interesting research in science education about how to teach the “Nature of Science” that addresses this. On a separate note, you might find some of Paul Feyerabend’s arguments against critical rationalism interesting.

    To which I replied:

    Exactly… A scientific “law” explains WHAT happens, while a scientific “theory” explains why.

    Water freezes at 0 degrees Centigrade is a “law”
    The theory that explains that would be that water freezes because the molecular movement is slowed enough that the molecules stick to each other and form ice crystals

    But as one might guess, this is just a step towards discussing the topic of evolution… By first defining certain terms and concepts (scientific method, theory, etc) I think a discussion of evolution vs fantasy (I mean creationism) will have less obvious roadblocks to stop it….

    And I’ll certainly check out more about Paul Feyerabend, thanks:-)

    I thought this raises an important point that I missed in my post: many people seem to have the mistaken impression that scientific theories become scientific laws.

    As Wikipedia states:

    A scientific law or scientific principle is a concise verbal or mathematical statement of a relation that expresses a fundamental principle of science, like Newton’s law of universal gravitation. A scientific law must always apply under the same conditions, and implies a causal relationship between its elements. The law must be confirmed and broadly agreed upon through the process of inductive reasoning. As well, factual and well-confirmed statements like “Mercury is liquid at standard temperature and pressure” are considered to be too specific to qualify as scientific laws. A central problem in the philosophy of science, going back to David Hume, is that of distinguishing scientific laws from principles that arise merely accidentally because of the constant conjunction of one thing and another.

    A law differs from a scientific theory in that it does not posit a mechanism or explanation of phenomena: it is merely a distillation of the results of repeated observation. As such, a law is limited in applicability to circumstances resembling those already observed, and is often found to be false when extrapolated. Ohm’s law only applies to constant currents, Newton’s law of universal gravitation only applies in weak gravitational fields, the early laws of aerodynamics such as Bernoulli’s principle do not apply in case of compressible flow such as occurs in transonic and supersonic flight, Hooke’s law only applies to strain below the elastic limit, etc.

    The term “scientific law” is traditionally associated with the natural sciences, though the social sciences also contain scientific laws. Laws can become obsolete if they are found in contradiction with new data, as with Bode’s law or the biogenetic law.

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  6. duckalogue says:

    Thank you for this post! It is just what I was looking for – a comprehensive explanation of the “scientific theory” vs “layman’s theory.”

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  9. jaleel says:

    Excellent. Well done.

  10. Collin says:

    I’ve never understood this insistence on rejecting concepts like “fact” and “truth”. I’ve also never understood why Karl Popper is considered, as it were, the founder or arbiter of science. I think this is one reason the IPCC scandal arose. There seems to be this idea that scientists have always been loyal followers of an exact method until now when they’ve been taken over by the politics demon (sarc).

    Scientists are people, just like everyone else. They don’t have a special purity that allows them to find good theories while everyone else flounders in ignorance. Indeed if they were, they would be the priesthood rightists imagine they are.

    The evidence is out there, and scientists find it and piece it together. Their ability to do this is due to the evidence itself being self-consistent, not the people. Some, like me, attribute that self-consistency to God. But that is our choice, not a necessary conclusion. We feel — however wrong it may be — that modern scientists are afraid to admit to an objective reality because of the fear that it would be an acknowledgment of what we call God. This is why otherwise liberal believers get up-in-arms about articles like this. If critical thinking is to survive, feelings like mine must be addressed head-on.

    I shouldn’t be ashamed to say that well-established scientific theories are facts. Especially in the case of evolution, when the slogan “evolution is not a fact” is used to attack science. I also shouldn’t be ashamed to say I believe in evolution, because this follows from my belief in the supremacy of evidence. To shy away from such pronouncements is, frankly, post-modern.

    • Jen says:

      Scientists always acknowledge that there are limitations to their research and evidence; these things are fluid and can change. As other areas of scientific understanding expand, (due to better observation, made possible by better technology, for example) evidence changes and so do theories.

      For example, global warming is a fact; it is a law of nature called the greenhouse gas effect. If gas molecules absorb energy, they will radiate that energy back out. Without the greenhouse gas effect, Earth’s temperature would be a balmy 0 degrees F. I want to say that ALL scientists agree on this; but that would be incorrect. If just ONE doesn’t, then I can’t say ALL. So, while most (99%?) of scientists agree that global warming occurs, there are several working theories which describe how this effect is occurring and how to measure the effect. Regrettably, the layman views this healthy, necessary disagreement among scientists the wrong way.

      It is incorrect to say a well established theory is a fact. When people state that “evolution is not a fact” they are making the mistake that this whole blog entry is about. The same mistake you are making when you say theories are facts.

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  12. jpgreenword says:

    Thank you very much for this detailed (and multi-sourced!) explanation of scientific theory and scientific law. As a high school science teacher, this will be very useful.

  13. Kari says:

    This post lets me know excatly what Theory is and what it means and lets me know in many many ways why and what i use it for like math and science.

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  18. Sean Ralph says:

    Sometimes two sets of theories and laws may exist in tandem. Both could be right and wrong at the same time. Greenhouse Gases could in theory exist both naturally and unnaturally at the same time producing the same outcomes or they could exist at different times producing once again the same outcomes.
    El Nino weather systems seem to be a naturally occurring event ( they were recorded by ancient Anztecs and Spanish Conquistadors) yet some scientists believe global warming has been responsible. In essence both theories could be right and co exist.
    Also data is only relevant to the field it records and is open to manipulation. This is both fact and fictional depending on how and why you use it. This data can be used in many varying contexts in and outside science and thus applied to many different genres.

    We believe we have all the known elements of the universe. These are the 98 we have naturally on earth, the other 20 made unnaturally (and growing as we use new techniques and better instrumentation). It could be argued in terms of Theories and Laws we are only at the beginning, that we have mastered the known facts and are now observing the unknown facts. We measure life from an Organic model based on absorption of sunlight (energy) into conversion of sugar based systems producing an output being life. These Laws of Physics follow similar Principles. But what if life was a constant or evolving entity, either using the Laws of Physics or not following them whatsoever. Our instrumentation would not be able to pick them up or even acknowledge their existence. Let us say the letter A which is made of three lines (depending on viewpoint), then we add a which has same meaning (depending on your viewpoint) and is made not 3 lines but 1 constant set of curves. Now ignoring the rules of Grammar for a moment both mean the same but from the untrained eye would be as vastly different as the letter x is to o. In fact a child with no knowledge would probably associate x with a than they would A with a. Yet we have conditioned ourselves automatically through education and laws and rules to know that A is not x or o but linked with a. It is how we have set the rules, how we define data and ultimately methods for reading and interpretation.
    We are not doing anything wrong as the process works for human understanding and our instruments such as computers. But what if there was another way of looking at something similar or even dissimilar, natural or unnatural.
    One amazing fact is we know more about our skies than our oceans and inner earth, yet these in theory exist in such quantities and abundance yet three miles into earth we know virtually nothing except what we can theorise or in simple English ‘Guess’
    So in time and with different and varying approaches and two think in totally novel and pre existing ways both human and computer we should be able to find new laws and theories. The problem will be in essence infinite as how many Laws of Physics are out there each correct and wrong, each measurable and immeasurable. Time will tell or will time itself be proven to exist, not exist or co exist.

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