In the comments on my post on Armstrong on Naturalism and Empiricism Brandon and JS raised a concern about the evolutionary argument I sketched against rationalism. I have hinted at this kind of argument before but I guess I have never spelled it out. I have sort of thought it was just too obviously an extension of Hume’s kind of argument…but maybe it is worth spelling out.
Suppose that you have a stable environment E. In E there are events (e1, e2,…en) and it so happens that there is a regularity in E such that e2 regularly and reliably follows e1. Now suppose that there are creatures, C, that live in E. Then evolutionary theory says (roughly) that C will adapt to E via natural selection (I do not mean to be saying that C will become optimally adapted, that is a hotly contested claim). One obvious source of reproductive advantage would be being able to track the regularities in E. If e2 is such that it is (harmful or) beneficial for C then it would, through the course of natural selection, come to be the case that C tracked the regularity, R, expressed by ‘e1 then e2’; that is to say C would come to associate e2 with the occurrence of e1. Now assume that R is some basic and (hitherto) extremely reliable regularity (like that when you have one object and you place another object next to it you then have two objects).
Now suppose that, for whatever reason, R continues to be regular and tokens of e1 are immediately followed by tokens of e2. Decedents of C will also track R, but will also have to track other regularities that they discover for themselves. So, decedents of C that have R ‘hardwired’ in will free up cognitive resources. So now suppose that C is a species from which a species evolved from which a species evolved…from which we evolved and that R has continued to be regular and reliable up till now. At this point R would presumably be something for which we are equipped to find intuitively obvious. This is exactly what developmental psychology (like work from Spelke and many others) has shown.
So, when the rationalist appeals to their experience of ‘finding something obvious’ as evidence that we know something in a special way that is revealed to be necessary and universal, it could just be the product of that regular and reliable conjunction of events has, around here and so far been that way. But that, of course, does not guarantee that it must be that way. Now how could the rationalist know which of the two theories better accounted for his experience? Our intuitions are shaped by the world that we happen to find ourselves in. And so if evolution is true rationalism is most likely false.
I’m also not sure evolution precludes intuition as evidence for rationalism. I suppose I just don’t think your reasoning pans out in real life. I don’t see how I can’t both agree with this: “we would expect that there would be certain truths which seem to be self-evident but are really just the product of a long process of natural selection in response to a stable environment”, and not believe in rationalism. Can’t I tell an equally nice just-so story like this: I agree with RB’s quote, but at a certain stage of complexity it’s been found that animals begin to intuit other actually self-evident beliefs, which then survive natural selection in virtue of their fitness. The end. I’m sure you disagree, however.
Well it would depend on what you mean when you say ‘animals begin to intuit self-evident beliefs’. If you don’t mean ‘discover solely by the use of reason necessary and universal facts about reality’ then we do not really disagree on anything. But if you do mean that, then the question is how could those kind of things be selected for or have any fitness at all if they did not causally interact with C or E? Sure there are spandrels and such, but in order for a property P to be reproductively beneficial it would have to play some role for C or in E. Notice that the mathematical truths play a hugely beneficial role for us. It is in fact their usefulness and indispensability to science that Quine and others have taken to show that they are empirical. David Rosenthal has given (in class) a similar argument for logic being empirical. He argued that one reason to think that it is is that it explains inferences that humans find valid and to that extent is hostage to the empirial–and so not analytic.
But maybe we did evolve to track necessary and universal facts about reality discovered by the use of reason. The point is that we couldn’t appeal to our experience of certainly as evidence for that view since we can’t rule out that the experience isn’t due to a very long association between certain events (that are not necessary). We would need some other kind of evidence. But what other evidence is there?