This thesis is a comparative analysis of Ibn Taymiyya of Damascus and Gregory of Rimini within their respective religious and philosophical traditions. Ibn Taymiyya and Gregory of Rimini rejected the use of Aristotelian logic in the valorization of divine revelation in Islam and Christianity respectively. The translation movements, in Baghdad and then in Toledo, ensured the transmission of Greek scientific and philosophical works to both the Islamic world during the 'Abbasid Caliphate and the Catholic Christian European milieu beginning in the eleventh century. By the fourteenth century both the Islamic and the Catholic European religious traditions had a long history of assimilating Aristotle's Organon. Ibn Taymiyya and Gregory of Rimini rejected the notion, adopted by the kalam and scholastic traditions respectively, that logical demonstration could be used to validate religious doctrine as taught in the Qur'an and the Bible. Ibn Taymiyya rejected demonstration completely but Gregory accepted its qualified use.