the most prominent French philosopher-theologian of the early 13th century and one of the first Western scholars to attempt to integrate classical Greek and Arabic philosophy with Christian doctrine.

William became a master of theology at the University of Paris in 1223 and a professor by 1225. He was named bishop of the city in 1228. As such he defended the rising mendicant orders against attacks by the secular clergy, which impugned the mendicants' orthodoxy and reason for existence. As a reformer he limited the clergy to one benefice (church office) at a time if it provided them sufficient means.

William's principal work, written between 1223 and 1240, is the monumental Magisterium divinale (“The Divine Teaching”), a seven-part compendium of philosophy and theology: De primo principio, or De Trinitate (“On the First Principle,” or “On the Trinity”); De universo creaturarum (“On the Universe of Created Things”); De anima (“On the Soul”); Cur Deus homo (“Why God Became Man”); De sacramentis (“On the Sacraments”); De fide et legibus (“On Faith and Laws”); De virtutibus et moribus (“On Virtues and Customs”).

After the condemnation of Aristotle's Physics and Metaphysics in 1210 by church authorities fearful of their negative effect on the Christian faith, William initiated the attempt to delete those Aristotelian theses that he saw as incompatible with Christian beliefs. On the other hand, he strove to assimilate into Christianity whatever in Aristotle's thought is consistent with it.

Influenced by the Aristotelianism of Avicenna (Ibn Sīnā), an 11th-century Islāmic philosopher, and by the Neoplatonism of Augustine and the school of Chartres, William, nevertheless, was sharply critical of those elements in classical Greek philosophy that contradicted Christian theology, specifically on the questions of human freedom, Divine Providence, and the individuality of the soul. Against Avicenna's determinism, he held that God “voluntarily” created the world, and he opposed those proponents of Aristotelianism who taught that man's conceptual powers are one with the single, universal intellect. William argued that the soul is an individualized, immortal “form,” or principle, of intelligent activity; man's sentient life, however, requires another activating “form.”

The complete works of William of Auvergne, edited in 1674 by B. Leferon, were reprinted in 1963. A critical text of De bono et malo by J.R. O'Donnell appeared in 1954.