It was through the Muslim philosophers Avicenna (980–1037) and Averroes (1126–98) that Europe came to know the works of Aristotle. From the ninth through the twelfth centuries the Muslim world was far more advanced in its knowledge of Greek philosophy than the West. The Muslim world had access to the chief works of Aristotle before Western Europe finally received them. The significance of Muslim philosophers was therefore twofold: they were transmitters of Aristotle and other Greek philosophers to the West, and they were also the authors of interpretations of Aristotle that became the basis of controversy in medieval philosophy.

Avicenna (which is a Latinized name for Ibn Sina) was a veritable polymath, with interests in logic, geometry, theology, and the Koran. Born in Persia, he was a child prodigy; he learned all the disciples and great works of literature as a young boy. He was extremely prolific: even while traveling a great deal, he wrote 160 books about a broad range of topics. At age sixteen he was influenced most by the Neo-Platonists and Aristotle.

God's Necessary Creation and Opposition to the Idea

Like Anselm, who argued that the definition of God as a “greatest conceivable being” implied his existence, Avicenna also thought that God's essence necessarily implied his existence. He coupled Anselm with Aristotle to arrive at his own doctrine of Creation.

According to Aristotle, everything that begins to exist must have a cause. Things that require a cause Aristotle called “possible beings.” A cause that is also a possible being must be caused by a prior being. This too must have a cause, and so on. But there cannot be an infinite series of such causes. There must therefore be a first cause, whose being is not simply possible but necessary, having its existence in itself and not from a cause, and this is God.

God is at the apex of being, has no beginning, is always active (i.e., in the Aristotelian sense of never being merely potential but always expressing his full being), and therefore has always created. According to Avicenna, then, creation is both necessary and eternal. Here came his controversial conclusion.

Since God was a “necessary being” and was without a beginning, Avicenna concluded that all God's attributes were necessary and without a beginning as well, including his status as the creator of the world. Thus God was not free in creating the world, for divine creativity is just another kind of activity and a necessary feature of his being.

If God and all his attributes are eternal, as Avicenna argued, then his creation of the world must have occurred from all eternity. Therefore, the world is eternal, although from all eternity it has depended on and emanated from God. Every creature is a necessary feature of a world system that could not be otherwise. Every existing thing is part of a logically determined chain of causes.

This conclusion struck Bonaventura in the thirteenth century as a serious error and in conflict with the biblical notion of Creation. According to Bonaventura, two chief features of Creation are that it is a product of God's free will, not of necessity, and that Creation occurred at a point in time, not from eternity. Aquinas would agree, however, that philosophically there is no way to decide whether Creation occurred in time or from eternity, that this must ultimately be a matter of faith.

A Muslim Who Defended the Philosophers

Averroes (Ibn Rushd) of Cordova was commended for defending the right of Muslims to study and incorporate Greek philosophy into the Islamic tradition. He was the most distinguished Arabian philosopher of the period. In fact, Averroes was renowned for trying to reconcile Aristotle's system of thought with Islam. Al-Ghazali (1058–1111) wrote an influential book called The Destruction of the Philosophers (sometimes translated as The Incoherence of the Philosophers). Ghazali argued with great passion that the philosophers contradict the Koran, each other, and themselves. He believed philosophical writings should be kept from the public, for “just as the poor swimmer must be kept from the slippery banks, so must mankind be kept from reading these books.”

Averroes responded strongly to Al-Ghazali's Destruction of the Philosophers with a thorough refutation in his work titled The Destruction of the Destruction. Elsewhere he had argued that Aristotle represents the apex and culmination of the human intellect and that his philosophy did not conflict with the Koran. For instance, he pointed out that the Koran presents the world as God's handiwork and concludes that this lets one demonstrate God's existence by showing God as the cause. In particular, Aristotle's logic, physics, and metaphysics provide people with the tools for such a demonstration, and Averroes cites Aristotle's argument for an Unmoved Mover as an example.

Despite such sound reasoning, Averroes's quarrel with religious traditionalists led to his being ostracized. His books were burned in Islamic Spain. To prevent any repeat instances of such “heresy,” a suppression of Greek philosophy was instituted. In 1195, at the age of sixty-nine, he was tried and exiled from his native Cordoba. But his reputation remains. His knowledge of Aristotle's texts was so respected by Christian scholars that he was given the honorific title “the Commentator of commentators” by late medieval philosophers.