The classical rationalist philosophical tradition in Arabic reached its culmination in the writings of the twelfth-century Andalusian Averroes whose translated commentaries on Aristotle conveyed to the Latin West a rationalist approach which significantly challenged and affected theological and philosophical thinking in that Christian context. That methodology is shown at work in his Fasl al-Maqāl or Book of the Distinction of Discourse and the Establishment of the Relation of Religious Law and Philosophy (c. 1280), although the deeply philosophical character of his subtle arguments has gone largely unappreciated. Here the philosophical foundations for his reasoning are exposed to reveal key elements of his rationalism. That approach is confirmed in his assertion in his later Long Commentary on the Metaphysics (c. 1290) that the highest worship of God is to be found first and foremost in the philosophical science of metaphysics rather than in the rituals of religion.