The topic of the article is the study of the relationship of reason and revelation in the philosophical approach of Thomas Aquinas, the Christian philosopher. The study highlights the most important foundations of Aquinas’s philosophical approach, especially the most important philosophical-theological issue. It is the relationship between reason and revelation, and how Aquinas attempted to use revelation and reason in order to found the most important Christian theological beliefs, how to make use of philosophy to explain those beliefs, how to defend Christian thought, theology and beliefs, and prove that it would not contradict reason. Moreover, the study discusses Aquinas’s reformative impact on Christian thought, and how he has quoted many philosophical issues from the Peripatetic school, especially the philosophical views of Ibn Sina (Avicenna). Aquinas also has greatly been affected by the views of Ibn Rushd al-Andalusi (Averroes), who had explained the philosophy of Aristotle. Therefore, the philosophy of Ibn Rushd and Ibn Sina is the original source of Aquinas’s philosophy that has overcome the whole Europe since the thirteenth century, especially in his attempt to synthesize reason and Christian revelation, or wisdom and the Shariah.