## Is Truth Necessary for Scientific Explanation?

24 01 2006

Over the last year or two I’ve become pretty convinced (though not necessarily for good reason) that inference to the best explanation (IBE) is the main (if not the only) tool of inference in non-deductive contexts. Even in mathematics I’d like to say this is the case, both in arriving at standard axioms, in supporting new ones, and in developing conjectures. (Of course, this is pending an account of explanation in mathematics.)

Anyway, some discussions I’ve had during that time with Peter Gerdes have made me wonder some more about the nature of explanation. He has on several occasions argued against the use of inference to the best explanation, making a claim something like saying that for something to be a good explanation presupposes that it is true, so we can’t recognize good explanations until after we’ve recognized the truth of the explainer.

Now, I don’t know the literature on this at all (I should probably look at this quite a bit before I decide to get around to graduating), so I don’t even know for instance what sorts of things A and B are supposed to be if A explains B. (Theories? Propositions? Facts? Events?) At any rate, it seems clear that you can’t explain something that didn’t happen, so B should be true (or actual, or whatever the appropriate property is for the sort of entity at question). However, I think this doesn’t seem so clear for A.

In ordinary usage, it does at first seem that A has to be true – I can’t explain why Mary is looking around on the ground by saying that she lost her wallet, unless she actually did lose her wallet. However, in the scientific case (and I would guess, the more complicated ordinary cases as well), it seems that good explanations really can come from false theories. For instance, Newton’s laws of gravitation and of motion explain Kepler’s laws of planetary motion (or at least, the data leading to his postulation of them) quite well – even though we all believe Newton’s laws don’t actually obtain. In fact, for this particular set of data, it’s not at all clear that relativity (or quantum gravity, or string theory, or …) is at all a better explanation just because it happens to be true (or closer to the truth).

There does seem to be something to the simplicity of the Newtonian explanation that makes it preferable. In addition, Newtonian mechanics is close enough to being correct that it seems to be useful as an explanation even though it’s actually false. That is, it helps us conceptualize what’s going on, make predictions about related facts, remember Kepler’s laws when we’re not literally memorizing them, and so on. There are very few senses in which saying “God is crying” is a good explanation for why it’s raining, and a lot more in which saying something not quite accurate about warm fronts and dew points and such is. If our notion of explanation wasn’t tolerant of falsehood in the antecedent, then science would rarely (if ever) help us explain anything – after all, we have good reason to believe that every scientific theory believed more than twenty years ago was false, which itself gives us good evidence to believe that current ones are false as well. However, it seems clear that science generally provides us better and better explanations of all sorts of phenomena, suggesting that false theories can in fact provide good explanations.

If explanation really is falsity-tolerant in the antecedent, as I think, then I think we can get IBE off the ground. Of course, we’d need to tell some story like what Jonah Schupbach was saying about a year ago at his blog, about why IBE tends to lead us towards the truth, even if it doesn’t presuppose it. And we’d have to watch out for the worries van Fraassen raises for using IBE as a supplement to probabilistic reasnong (which I learned about from a post by Dustin Locke on his blog). I think these are compatible, if Jonah is right that IBE is just a heuristic for simplifying bayesian computations, rather than a supplement to them as van Fraassen supposes. But we’d need to work things out in more detail of course.