In response to Pascal's famous wager argument for adopting Christian belief, Denis Diderot noted that ‘An Imam could just as well reason this way’. In this article, I will show how Diderot's observation about Pascal's argument can legitimately be made about Alvin Plantinga's Reformed Epistemology (RE) and its use in defending the rationality of Christian belief. Plantinga's RE can, with some minor adjustments, easily be adopted by Muslims. I shall argue that an Islamic analogue of Plantinga's Christian RE presents an undercutting rationality defeater for Christian belief for those reflective Christians who adopt Plantinga-style religious epistemology. I call this defeater the ‘Diderot Objection’ to Plantinga's RE. As part of my discussion, I will consider how Plantinga attempts to respond to this sort of objection and will show why his response runs into difficulties.
