William of Champeaux

Guillaume de Champeaux (; 18 January 1121), known in English as William of Champeaux and Latinised to Gulielmus de Campellis, was a French philosopher and theologian.

Biography William was born at Champeaux near Melun. After studying under Anselm of Laon and Roscellinus, he taught in the school of the cathedral of Notre-Dame, of which he was made canon in 1103. Among his pupils was Peter Abelard, whom he had a disagreement with because Abelard challenged some of his ideas, and because William thought Abelard was too arrogant. Abelard calls him the "supreme master" of dialectic after he replaced his master as the new teacher. In 1108 he resigned his positions as archdeacon of Paris and master of Notre Dame, and retreated to the shrine of St Victor, outside the city walls of Paris, where, under his influence, there formed what would become the abbey of St Victor.

He was a friend of Bernard of Clairvaux, having helped Bernard recuperate from ill-health; later he motivated Bernard to write some of his important works including the Apologia, which was dedicated to William. In the last of these he maintains that children who die unbaptized must be lost, the pure soul being defiled by the grossness of the body, and declares that God's will is not to be questioned. He upholds the theory of creationism (i.e., that a soul is specially created for each human being). Félix Ravaisson has discovered a number of fragments by him, among which the most important is the De Essentia Dei et de Substantia Dei; a Liber Sententiarum, consisting of discussions on ethics and scriptural interpretation, is also ascribed to Champeaux.