The dissertation posits that the late works of Fakhr al-Dīn al-Rāzī (d. 606/1210) portray knowledge as central both for the perfection of the soul and for the achievement of eternal felicity in the afterlife. To fully explore this thesis, the dissertation researches distinct topics as explored in Rāzī’s later corpus with a focus on Rāzī’s last work, al-Maṭālib al-ʿāliya, including human epistemology, syllogistic reasoning, spiritual inspiration, magic and miracles, cosmology, the soul, and the afterlife. The first chapter explores the two primary paths to knowing as posited by Rāzī, namely, theoretical reasoning and spiritual striving (or, ideally, the combination of the two). Knowledge acquisition through theoretical reasoning is the subject of the second chapter, which discusses the process and importance of syllogistic reasoning in Rāzī’s later works. Given that the celestial realm is fundamental for the reception of knowledge as achieved through spiritual striving, the third chapter of the dissertation explores the structure and function of Rāzī’s cosmology particularly as it relates to divine inspiration, revelation, and human perfection. The topics treated in this chapter are the widest ranging of the dissertation, as the existence of celestial beings and their relation to humankind allows not only for the prophet’s access to divine knowledge and his production of miracles but also for the existence and efficacy of the occult sciences. Finally, the fourth and final chapter of the dissertation brings together these strands of research into Rāzī’s discursive and non-discursive epistemologies to discuss the importance of knowledge for the perfection and felicity of the human soul. The chapter first discusses Rāzī’s views of the nature of the soul as presented in his later works and then addresses the nature of the afterlife and the effects of knowledge acquisition on the eternal life of the soul. Each chapter also explores other intellectual thinkers and trends as they relate to distinct concepts and arguments, locating sources of influence not only in the Islamic theological and philosophical traditions but also in the Corpus Hermeticum, texts (pseudo and authentic) of the Greek philosophical tradition and the portrayal of these figures in Islamic works, and in the writings of the Ikhwān al-Ṣafāʾ.