In Chapter 12 of Warrant and Proper Function, Alvin Plantinga constructs two arguments against evolutionary naturalism, which he construes as a conjunction E&N. The hypothesis E says that “human cognitive faculties arose by way of the mechanisms to which contemporary evolutionary thought directs our attention” (p. 220). With respect to proposition N, Plantinga (p. 270) says “it isn't easy to say precisely what naturalism is,” but then adds that “crucial to metaphysical naturalism, of course, is the view that there is no such person as the God of traditional theism.” Plantinga tries to cast doubt on the conjunction E&N in two ways. His “preliminary argument” aims to show that the conjunction is probably false, given the fact (R) that our psychological mechanisms for forming beliefs about the world are generally reliable. His “main argument” aims to show that the conjunction E&N is self-defeating – if you believe E&N, then you should stop believing that conjunction. Plantinga further develops the main argument in his unpublished paper “Naturalism Defeated” (Plantinga 1994). We will try to show that both arguments contain serious errors.