Field of Science

On theory and hypothesis

This article in the Washington Post is very tough in creationism, which I can only agree with. For example:
Evolution could not have produced a single mother and father of all future humans, so there was no Adam and no Eve. No Adam and Eve: no fall. No fall: no need for redemption. No need for redemption: no need for a redeemer. No need for a redeemer: no need for the crucifixion or the resurrection, and no need to believe in that redeemer in order to gain eternal life. And not the slightest reason to believe in eternal life in the first place.
It's a great thing to read in such a prominent newspaper.

However, the author, Paula Kirby, also reiterates a characterization of 'theory' and 'hypothesis' that I vehemently disagree with:
In everyday English, 'theory' can mean something vague, a hunch, a guess. In scientific English, it is almost as far from that meaning as it's possible to get: in science, a theory is the best explanation for a set of facts. It carries real weight: in science, nothing can be called a 'theory' until it is very well established indeed. Science has its own term for what, in a non-scientific context, the rest of us might call a 'theory': the scientific term for a suggestion, a best guess, something that seems plausible but has not yet been shown to be reliably true, is 'hypothesis'. You will never, ever hear a scientist talk about 'the hypothesis of evolution', for the simple reason that evolution is long past that stage. Evolution is a theory in the scientific sense of the word - tested, researched, explored and supported by masses and masses of evidence. There may still be specific details that are not entirely agreed upon; but the fact of evolution itself is not disputed by any reputable scientist.
It's a common misunderstanding that those two words convey degrees of certainty in science. They do not. A theory need not be "very well established", and a hypothesis is not necessarily something that has "not yet been shown to be true".

Rather, in science, a theory specifies a cohesive explanation of a natural phenomenon. A theory is a model of how something works, and can produce several hypotheses that can be tested. For example, gravity is a theory of how masses attract each other and other related phenomena (and it is a fact that the phenomenon of gravity exists), and one hypothesis that comes from that theory is that that a hammer dropped above the surface of the moon will fall down to the surface. But again, neither theory nor hypothesis need to be true to be called theory and hypothesis. There are theories that have been shown to be wrong, and yet we still call them theories. The theory of the ether has been shown to be wrong, but it is still a theory. The theory of homeopathy has been shown time and again to be false, and yet we can still refer to it as a theory.

Similarly, a hypothesis need not be a tentative statement of fact. It is a hypothesis that a hammer will fall down to levitate over the moon, but even when that hypothesis has been tested, it is still a hypothesis. It is a disproven hypothesis, but nonetheless still a hypothesis. In everyday English, it does indeed connote uncertainty, but not so in science. For example, we can still refer to both the 'null hypothesis' and our pet hypothesis even when the evidence favors one of them over the other. It's a hypothesis that the hammer will levitate, and while it has been shown to be false, but it can still be termed a hypothesis.

At least, this is how I use the words, and I am a scientist (but see impostor syndrome).


  1. Heh, I noticed the same thing (I think the phrase "best explanation" made the error particularly blatant in this column, and hard to miss). I think she is right, though, to say that a theory can't really be something "vague"... A theory can be dead wrong, but it should at least make predictions and have some sort of order to it.

    Which is why Creationism is not even a theory. You mention homeopathy; I think that is right on the border. It has just enough of a structure to it to maybe qualify.

    In any case, I think it conveys the meaning well enough for a lay audience. But yeah. I agree.

  2. I tested your hypothesis again and indeed the hammer did not fall to the moon. That reinforces your result that the hypothesis is disproved (though I detest the proved/disproved terminology). However, with a hypothesis like the one you suggest, we should not discount it out-of-hand. I can easily envision examples where I drop a hammer and it falls to the moon, such as if I were standing on the moon when I dropped the hammer. I only bring this up, because it shows the tentativeness and constant refining of hypotheses/theories/etc. in science.

  3. People only want to memorize the theory or hypothesis in the easiest way. So people named new discoveries/hypothesis whatever they seemed to be, when their work were most known/famous to the public.In this way the theory/hypothesis would spread fastest. But the standard or definition of theory or hypothesis is still as the article in Washington Post said. I bet no one would make a dead true fact as a hypothesis but a theory when they were 100% sure it would be the truth, and when this theory is found to be wrong, we'd still call it a theory.

  4. Lorax, if you are trying to say that one test of a hypothesis that goes against the larger theory doesn't automatically disprove the whole theory, then I agree, of course.

    If the hammer really doesn't fall to the moon, then there still might be some explanation that doesn't disprove the theory. Perhaps a magnetic field set up by a jesting astronaut?

    So, B, you really think that we would ever call it a theory that the hammer falls to the moon? I would be glad to call it a fact that the hammer falls, but could not imagine ever referring to that as a theory.

  5. A better description of this than my boiler-plate. You just *know* I'm so going to knick this now! (And I hope I will remember the source. :-/)

    Btw, my hypothesis is that there is some confusion between hammers levitating and falling in the last paragraph. I base that on the theory of "communication", FWIW. :-)

  6. Thorbjörn, fixed the error in the last paragraph. Thanks.

  7. It seems a bit petty to pick up on the (admittedly mistaken) distinction between a scientific theory and scientific hypothesis when the thrust of the 'distinction' argument was simply to show that there is an important distinction between colloquial 'theory' and scientific 'theory'; which the article succeeds in doing.


Markup Key:
- <b>bold</b> = bold
- <i>italic</i> = italic
- <a href="">FoS</a> = FoS