The North African scholar Muhammad ibn Yusuf al-Sanusi (1436-90), from Tlemcen, present-day Algeria, was one of the most influential theologians and logicians in the Islamic tradition. al-Sanusi's theological works were wildly popular in large areas of the Islamic world until the modern period and are still studied to this day. In the premodern period, his works were translated or adapted into Berber, Fulani, Turkish, Malay, and Javanese. The sheer number of commentaries, glosses, adaptations, and versifications of his works in subsequent centuries is testament to their popularity. Despite this historical influence, contemporary studies on al- Sanusi have been sparse. In this book, author Khaled El-Rouayheb surveys al- Sanusi's life, writings, and intellectual milieu, including discussions of his controversial attacks on imitation or conformism to one's elders and peers when it comes to religious belief and his insistence that every sane believer should learn both the core articles of faith and their rational groundings. Closely analyzing al- Sanusi's logical writings--especially the influential Epitome of Logic -- and interventions in long-standing topics in Islamic theology, El-Rouayheb traces and the reception of the revered theologian's works down to the modern period.