The acknowledged leader of those who interpreted Aristotle through the eyes of Averroës, in 13th-century Paris. Dante puts him in the circle of wise men in Paradise, and has his praises sung by Aquinas, which puzzles commentators, since the Averroists were amongst Aquinas’s opponents. Siger shows himself well aware of the non-Aristotelian nature of Aquinas’s notion of existence. His principal treatise was On the Necessity and Contingency of Causes, condemned in 1277 as denying freedom of the will.