I have always thought that the two questions respecting God and the Soul were the chiefs of those that ought to be determined by the help of Philosophy rather than Theology. for although to us, the faithful, it is sufficient to hold as matters of faith, that the human soul does not perish with the body, and that God exists, it yet assuredly seems impossible ever to persuade infidels of the reality of any religion, or almost even any moral virtue, unless, first of all, those two things be proved to them by natural reason. (Descartes in Popkin 1966, p. 122).It can be seen that Descartes’ aim in offering the Meditations was precisely to provide rational proof for accepting the belief in God and the Soul, that is, rational proof that is sufficient to convince even the infidels.However, behind all the discussions on a rational proof for God’s existence lies the inherent dualism of Descartes. In this paper, the author examines Descartes’ dualism by taking into account his philosophical project as outlined in the Meditations on First Philosophy. The author then outlines Gilbert Ryle’s critique of Cartesian dualism, revolving around Ryle’s argument that the latter rests on a category-mistake.To examine Descartes is to examine the rationalist enterprise. It is within this context of searching for epistemological certainty that Rene Descartes’ philosophical enterprise should be examined. For while he sought to provide a proof for God’s existence, and in which case his endeavor became a theological work of some sort, his proffered proof is primarily a work in rationalist epistemology. In trying to establish what ought to be considered as the reliable foundation of one’s beliefs, Descartes began his rational inquiry by doubting everything that can be doubted. It is only rational as per Descartes, to base all beliefs upon a foundation that cannot be doubted. Hence, he assumed that if he can arrive at that belief which can no longer be doubted, then he would have arrived at the only reliable foundation of knowledge.