C. S. Lewis was perhaps the most popular and influential Christian apologist of the 20th Century, and his work is full of philosophical themes and arguments. Despite this, the main body of Lewis' work has received only scant attention from academic philosophers. Although countless books and articles have been written about C.S. Lewis and his writings, we are without a balanced and sustained evaluation of the philosophical themes and arguments to be found in his works. This is unfortunate for, in the words of James Patrick, the philosophical aspects of Lewis' work "constitute the very texture of his apologetic". It is hoped that this dissertation goes some way towards changing the situation. The dissertation contains five mam chapters, addressing four issues in the philosophy of religion through the writings of C.S. Lewis. Those issues are: the Euthyphro dilemma, the philosophical status of miracles, the Freudian critique of religious belief, and an argument from Lewis that has been dubbed 'the argument from desire'. While disagreeing with Lewis in some of the details, the dissertation defends a broadly Lewisian (and therefore broadly Christian) approach to each of these issues. Indeed, these Lewisian positions are defended with refurbished versions of Lewis' own arguments. In addition to a summary of some of the philosophical themes and arguments from C.S. Lewis that are not addressed in this dissertation, the work also includes two appendices. Appendix A is a short biography of C.S. Lewis. Appendix B offers a few thoughts on Lewis' general stance on the relation between faith and reason.