This paper argues, not that physicalism is wrong, but that it is irrational. The paper defines standards of rationality, both metaphysical and epistemological, that physicalism necessarily inherits from science. Then it assesses physicalist efforts to naturalize consciousness in light of these. It concludes that physicalism allows its metaphysics to outrun its epistemology, in defiance of applicable standards, revealing a fundamental incoherence in the doctrine. The paper also briefly reviews other naturalization programs, to claim that physicalism, unlike the sciences, hasn't proved fruitful.