Siger de Brabant (sēzhāˈ də bräbäNˈ) [key], fl. 1260–77, French theologian, head of the movement known as Latin Averroism. At the Univ. of Paris he taught that the individual soul had no immortality and that only the universal "active intellect" was immortal. He maintained also that the world had existed from eternity. In an attempt to reconcile these beliefs with Christian faith, Siger adopted the Averroist notion of "double truth"—that something could be true in rational philosophy but false in religious belief. St. Thomas Aquinas vigorously attacked Siger's teachings, and the doctrines were condemned in Paris in and after 1270. Siger died in Italy.