Averroes was aware that Arabic and Andalusian astronomers of his time focused on "mathematical" astronomy, which enabled accurate predictions through calculations but did not provide a detailed physical explanation of how the universe worked. According to him, "the astronomy of our time offers no truth, but only agrees with the calculations and not with what exists." He attempted to reform astronomy to be reconciled with physics, especially the physics of Aristotle. His long commentary of Aristotle's Metaphysics describes the principles of his attempted reform, but later in his life he declared that his attempts had failed. He confessed that he had not enough time or knowledge to reconcile the observed planetary motions with Aristotelian principles. In addition, he did not know the works of Eudoxus and Callippus, and so he missed the context of some of Aristotle's astronomical works. However, his works influenced astronomer Nur ad-Din al-Bitruji (d. 1204) who adopted most of his reform principles and did succeed in proposing an early astronomical system based on Aristotelian physics.