Rorty (in Lepore, ed., Truth and Interpretation, 1986) claims that the concept of truth does not enter into explanations. Suppose, however, that I observe physicians and magicians attempting to cure diseases. I notice that the physicians are often successful, while the magicians are no more successful than chance. Moreover, suppose that I know nothing about the actual disciplines of medicine and magic. I might, nonetheless, form the explanatory hypothesis that:
- Physicians are more effective at healing because their beliefs about the causes of diseases are more often true than those of the magicians.
Rorty considers simpler versions of this sort of explanation (he considers the case of a person getting a destination because he knows where it is), and thinks that those are only "promissory notes for explanations", and that the full explanation will say what the contents of the beliefs are, without the need to refer to truth. Thus, Rorty thinks that (1) is enthymematic (that much is obvious—there is a lot of background assumed in (1)), and indeed enthymematic for an explanation that makes no reference to truth. Presumably this expanded explanation is something like this:
- Physicians are more effective at healing because physician A believes that gout is caused by elevated levels of uric acid, and gout is caused by elevated levels of uric acid, and physician B believes that ..., and ..., and magician X believes that gout is caused by demons, but gout is not caused by demons, ..., and 'A, B, ...' is a list of most physicians, while 'X, Y, ...' is a list of most magicians.
It is a mistake, however, to take (1) to be enthymematic for (2). One reason is that the inference to (1) was an instance of inference to best explanation, and was an inference that one could make without anything like the sort of information involved in (2). A different reason for this is that we lose important explanatory information in passing from (1) to (2). We miss the regularity about physicians' and magicians' beliefs that is expressed by (1), a regularity that is not merely coincidental but itself explained, e.g., by the physicians' employment of the scientific method and the magicians' adherence to a secrecy that makes intersubjective testing impossible.
To take (1) to be enthymematic for (2) would be relevantly like replacing the explanation:
- About half of the coins I tossed landed heads because the outcomes of the throws are independent random variables, with probability 1/2 of landing heads, and hence it is statistically likely that approximately half of the coins I tossed land heads,
- About half of the coins I tossed landed heads, because six is about half of ten, and coin 1 landed heads, coin 2 landed heads, coin 3 landed tails, coin 4 landed tails, coin 5 landed heads, coin 6 landed heads, coin 7 landed heads, coin 8 landed heads, coin 9 landed tails and coin 10 landed tails.
The point has been made, in a somewhat different way, by Hartry Field. And Kitcher has run a similar argument, too. There is nothing original about the basic argument, but I think the comparison to (3) and (4) is illuminating.
Corollary: Truth enters into explanation of physical facts. But if it enters into explanation of physical facts, then either naturalism is false, or truth is a natural property. The prospects for seeing truth as a natural property are poor—that is something we see from the literature on truth, as well as from the fact that if truth were a natural property, then presumably a liar sentence could be formulated in the (first-order? I think so!) language of science. Hence naturalism is false.