I know that between scientists they make a distinction between hypothesis and theory. They usually say that hypothesis is something unconfirmed, and theory is something more confirmed (or falsified).

Is there a philosophical basis for this definition? Or is it just a useful simplification for everyday life?

I think a theory simply means something more complex, having evidence or not. I may have a completely false theory, but it would still be a theory, because it involves a set of hypotheses and propositions.

  • For non scientific speech, a theory is like a guess, or a hypothesis. In science speech, a theory is well substantiated have gone from some to extensive experimental justification. Commented Aug 7, 2017 at 21:28
  • 1
    A (physical) theory is a reasonably broad explanatory model that ties together an entire regime of observable phenomena, like Maxwell's theory of the electromagnetic field. A (physical) hypothesis typically refers to a more narrow range, or just single, phenomenon, like the non-existence of magnetic monopoles. In this example, that hypothesis (among many others) is subsumed by Maxwell's theory.
    – user19423
    Commented Aug 8, 2017 at 6:32
  • As the range of answers here suggests, the terms hypothesis and theory are used in several different ways. All those different definitions are useful for different purposes. For example, sometimes we need to distinguish unconfirmed and well-confirmed statements; other times we need to distinguish statements with broad or narrow scope. So the question "is this the right way to distinguish hypotheses from theories?" is underspecified. What purpose is the distinction supposed to serve in the context you're thinking about?
    – Dan Hicks
    Commented Aug 8, 2017 at 14:45

5 Answers 5


I think your own understanding is a good one. Perhaps the meaning of theory shows up particularly clearly when we think of how science in general will probably always be conducted with a kind of background theory about the way the world is; in philosophy, our background theory will determine the kinds of terms we consider valid in generating hypotheses, for example the logical positivist philosopher could consider that metaphysical propositions necessarily have no correspondence with circumstances in the world - and so, on the grounds of her theory, regard hypotheses as valid only when they are not framed in metaphysical terms. But, in this case, perhaps the logical positivist philosopher is elevating what is virtually no more than an hypothesis to the level of theory - in which instance, perhaps, she has failed to recognise the difference in hypothesis and theory you mention, that if something is to be regarded as theory it ought at least to purport to give a somewhat complex background explanation of the phenomena in question, against which to test hypotheses with evidence.


A key concept in science is the ability to consider any hypothesis, no matter how radical. If you wished to suggest the hypothesis that the moon is made of cheese, you are absolutely within your right to do so. However, they also need something which can describe a product of their scientific endeavors which has some meaningful value. These products are typically more abstract that the raw hypotheses that got tested, and they have substantial evidence suggesting that they may be true. These get called "theories." If you wanted to claim that you had a theory that the moon was made of cheese, I'd call you on it, demanding to see your evidence.

In between is a very murky ground. There's definitely no clear dividing line between a hypothesis and a theory. A hypothesis may be too narrow to earn the title of a theory, even if it is heavily tested. An abstract idea may be insufficiently tested to call it a theory. As such, I would say the definitions you provided are simplifications for every day life, but they aren't far from the truth. They just miss out on the exciting process of actually turning a hypothesis or hypotheses into a theory.

If you are willing to consider subjective differences, one difference you can rely on is that if you have a "theory," at least someone believes enough evidence has been collected to believe the theory is true. Typically it implies that the speaker believes it to be true, though that is not always the case (e.g. creationists may talk about "evolutionary theory," but from their word choice, you'll know they don't actually believe it themselves)


I hope it's acceptable to discuss just one philosopher in my answer because he did a lot of thinking about these issues. W.V. Quine sets out six virtues of plausible hypotheses: conservation, modesty, simplicity, generality, refutability and precision.

These are virtues (ideal hypotheses), very much to Quine's taste. Which is rather funny since Quine likes to demand empirical evidence for everything, and I don't know if all these virtues can be supported by empirical evidence. They sound suspiciously rational to me, that is, they sound like they were generated wholly by mind. And even worse for Quine, they sound like just matters of taste!

In the real world, I think scientists get their hypotheses from many areas, dreams, hunches, etc., and of course there are fortuitous (read, lucky) accidents in the lab that result in great new discoveries and theories.

I guess a scientist could whip-up a beautiful, virtuous hypothesis after the fact to satisfy Quine's six virtues.

Nevertheless, I think Quine still has something to offer to the scientist when he speaks about theories and other things. Theories he says are underdetermined by the evidence because when we reduce them to language we extend them, so that not all of the theory is supported by empirical evidence.

Now even though our sound scientific theories are underdetermined, they still can be a fact of the matter. He specifically mentions physics in this connection.

Why are they a fact of the matter? " Because good theories are the simplest theories that account for all the evidence. These entities and their properties and interrelations (which make up theories) are all there is to the world, and all there is to be right or wrong about." Dagfin Follesdal on Quine.

So I would say that for Quine the good theory would be based on empirical evidence, it would be as simple as possible but still take into account all of the evidence.

To Devanil, then I would answer that the hypothesis in the "real world" might be even a guess, a hunch, the scientist has an idea and this sends him to the lab to test it! Regarding theories, I follow Quine in thinking we need empirical evidence for them. However, when we talk or write about theories we are likely to extend their claims beyond what the evidence strictly allows.

Finally, there are facts of the matter in science, but not in other things we study (Quine would say). Of course this does not mean that scientific theories cannot be revised. Certainly they can. All Quine is suggesting in that science (and specifically) physics can offer a fact of the matter, at least for the time being until such a theory may be revised.

Ref: Gibson, Roger F. Jr, (1988), Enlightened Empiricism: An Examination of WV Quine's Theory of Knowledge, U South Florida, Tampa. Great book that pulls Quine's scraps together and makes sense of them.


Theories are collections of related assumptions (together with their direct implications, since we assume logic always applies.) A given theory gives an explanation for a corresponding body of data, to which it gives a consistent interpretation. Theories come in all scales, from the single hypothesis to the underlayment for an entire science during a given developmental period, called a paradigm.

We are most often concerned with the smallest collection of hypotheses that can be tested together. When we say things like the theory of evolution, or the theory of gravitation, or the theory of cognitive dissonance, we tend to mean a package like that. Since these things only become testable together, you have to take or leave the package as a unit almost all of the time.

Phenomena are not testable individually. One needs enough other assumptions to put them in context and have them make sense. You cannot test the value of the gravitational constant, for instance, in isolation. You need Newton's laws of motion, you need various understandings about materials and friction, you need the assumption that your means of measuring times and masses are reliable, which may entail a dozen other assumptions...

Only once all those other things are tied together (backing up the idea that the gravitational constant, g, exists and has a value at all) can the hypothesis that the value of g is close to a given number be tested. But all of these things are parts or consequences of the basic paradigm of Newtonian physics, which holds up the theory of gravitation, in the context of which your actual hypothesis about a single number can be considered meaningful.

At the same time, the whole of Newtonian physics preceding gravity, including inertia, acceleration, constancy of mass, preservation of energy, etc. could be true, and gravity could work in some other way. But what you have to add to the theory to explain gravity itself and constitute a testable network of assumptions is not a single observation. It is compound, including the inverse-square law, the mutuality of attraction, the independence of the attraction from different materials and configurations, etc. So it is convenient to break off gravitation as a separate sub-theory of the Newtonian paradigm and to discuss the theory of gravitation as an entity of its own.


I think it's a little bit more than that and there's some quirk of language going on

A hypothesis is an attempt to explain something, It can forever exist as a hypothesis

A scientific theory is something that is true for the set of known facts. The theory only becomes false when there are facts that arise that falsify that theory. At that point it no longer is a scientific theory, it becomes superseded or obsolete and can't be regarded as a scientific theory in anything other than the past tense ( we just don't have a word for a false theory ).

So I think its a bit of a language issue that a false theory is not the same as a scientific theory. Kind of like if we didn't have the word hypothesis we might use "proposed theory", then we may confuse it with scientific theory ( which people do anyways )

So when you say " I may have a completely false theory, but it would still be a theory, "

you don't. It's just like a "not a dog" isn't a dog. It just doesn't pass the tests of what a dog is. You may have had a cat that looks like a dog, you call it a dog, but then you find out it's a cat, you can't still claim the cat is still a dog. You could only say it is an animal I once thought was a dog.

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