Averroës, the last of the great Islamic philosophers, lived roughly one hundred fifty years after Avicenna, his philosophic rival, and about three generations after al-Ghazzali, the greatest of Muslim theologians. In his controversy with these two men, he concerned himself primarily with the defense and purification of Aristotle, whom he followed as closely as he could. Because he, too, accepted such spurious works as Theologia Aristotelis (derived from Plotinus), his interpretation is still permeated by Neoplatonic elements, but to a lesser extent than that of Avicenna. The success of his endeavor is indicated by the fact that he was known to Scholastic writers as the Commentator and that no less a person than Saint Thomas Aquinas had him constantly at hand as he wrote his Summa contra gentiles (c. 1258-1260; English translation, 1923) and his various commentaries on Aristotle.
The Incoherence of the Incoherence was written in reply to mystic al-Ghazzali’s book, Tah-fut al-falsifa (1095; Incoherence of the Philosophers, 1958), in which al-Ghazzali attacked the philosophers, and in particular Avicenna, for advocating doctrines that were incompatible with their faith. As the title of his own book suggests, Averroës came to the defense of the philosophers. Adopting a position similar to that of the later medieval thinkers who distinguished between revealed and natural theology, Averroës scrupulously avoided denying any tenet of his faith; nevertheless, he sided firmly with the philosophers. His interpretations of religious doctrines were so far removed from those of the theologians that even though he was studied carefully by Hebrew and Christian philosophers, he was not recognized to any great extent by his Islamic contemporaries. Averroës’s book plays a very important role in the long controversy between the philosophers and the theologians because it is concerned chiefly with the nature and existence of God and with the relationship between God and the cosmos. Averroës does not spell out his position in detail, for he agrees on the whole with the earlier commentators on Aristotle and with the version of Aristotle he receives from them. In particular, he agrees largely with Avicenna, disagreeing on those points, and they are important points, where he thinks Avicenna departs from Aristotle.