The purpose of this paper is to establish the claim that Searle's version of biologicalnaturalism, articulated in Rediscovery and defended elsewhere, is an incoherent theory of themind. I attempt to make good on this claim by showing (i) that Searle's biologicalnaturalism is committed to four claims which are individually plausible but not possiblefor Searle to hold simultaneously, (ii) that Searle's biological naturalism is, despiteSearle's protests to the contrary, a form of dualism, and therefore (iii) that Searle'sbiological naturalism is enmeshed in the same philosophical tradition from whichSearle claims to be departing, and finally (iv) that Searle's commitment to the jointnotions of nonreductivism and causal closure of the physical domain creates a problemhis theory of the mind lacks the resources to solve plausibly.