Alvin Plantinga argues that a natural way to understand such notions as rationality and irrationality is in terms of the proper functioning of the relevant cognitive equipment. Seen from this perspective, the question whether it is rational to believe in God without the evidential support of other propositions is really a metaphysical or theological dispute. The theist has an easy time explaining the notion of our cognitive equipment's functioning properly: our cognitive equipment functions properly when it functions in the way God designed it to function. The atheist evidential objector, however, owes us an account of this notion. What does he mean when he complains that the theist without evidence displays a cognitive defect of some sort? How does he understand the notion of cognitive malfunction?