Tuesday, August 31, 2010

Reducing Hesperus

Does a reductivist or 'identity' theory have to be eliminativist? Perhaps not. The theory could simply be asserting an identity. Take an early scientific discovery: the heavenly body that appears in the morning (Phosphorus) is identical with the heavenly body that appears in the evening (Hesperus). Is the theory that Hesperus = Phosphorus a reductivist theory? Nothing has been eliminated. Hesperus has not been eliminated because Hesperus is identical with Phosphorus, and Phosphorus has not been eliminated. By equal reasoning, Phosphorus has not been eliminated. So nothing has been eliminated. But is the theory reductivist? It seems to be lacking the asymmetry that we expect of a properly reductivist theory. It seems reasonable to assert that mental states are really brain states. But if this were merely an identity statement like Hesperus = Phosphorus, it would be just as reasonable to assert that brain states are 'really' mental states. Which seems odd.


David Brightly said...

Does this amount to a case of theory change? It seems there is no change in the belief as to what heavenly bodies are, just recognition that some double-counting has taken place. Like miscounting the teaspoons. But this is to use the modern concept of planet. If the ancients thought of the planets as gods, all with different characters, they may have felt that some more explaining was called for.

Edward Ockham said...

>>Does this amount to a case of theory change?

Well that's the question. Someone at Bill's place sought sought to evade the consequence that all reduction involves elimination by claiming that simple identity does not involve elimination. He is right, but then is simple identity a theory change? Probably not, as you point out.