In this monograph, Ahmed Oulddali investigates the psychological and epistemological ideas which underlie Fakhr al-Dīn al-Rāzī’s speculative exegesis. Known as one of the few Muslim theologians to have proposed a philosophical interpretation of the Qurʾān, Rāzī appears here as an innovative thinker, deeply convinced of the need to rely on rational methods to understand revelation. His formal rejection of literalism and his multiple borrowings from Avicenna’s philosophy are explained as a consequence of a theory of knowledge in which reason plays a decisive role. Indeed, the numerous comparisons made show that, unlike other Sunni theologians and exegetes, Rāzī develops an open conception of reason that includes philosophical reflection and does not exclude it. The application of this original conception makes the hermeneutics proposed by him in al-Tafsīr al-Kabīr (Mafātīḥ al-ġayb) naturally receptive to ideas and concepts derived from the various branches of the rational sciences, including metaphysics. This book deals with numerous other fundamental issues related to psychology, noetics, perception, prophecy and eschatology. It also discusses the definition of several key notions, such as soul, science, reasoning, evidence, certainty, doubt, and so on. Even if it is devoted to the Qu’ranic commentary, this study uses most of Razi's published works. For one of the objectives pursued is to know how this author applies his methods not only in exegesis, but also in the other fields of knowledge dealt with in his writings, like theology and legal theory. Richly infused with illustrative texts and original translations from Arab sources, this monograph offers an overview of the philosophical, theological and exegetical issues to which the thought of Rāzī responds.