1612-1694. French theologian and philosopher. He is generally considered the foremost member of a distinguished French family, a number of whom embraced Jansenism* and exercised a formative influence over the movement. Born in Paris, he first studied law and later theology at the Sorbonne. In 1638, influenced by his mother, he placed himself under the spiritual tutelage of the Abbé de Saint-Cyran* (d.1643) who was a close friend of Cornelis Jansen (d.1638) and at that time chief apostle in Paris of the movement Jansen founded. Saint-Cyran encouraged Arnauld's ordination as priest in 1641 and inspired him to write his first major work entitled De la fréquente communion in 1643. The book provoked a storm of protest from the Jesuits and established Arnauld as the head of Jansenism in France after Saint-Cyran's death. Arnauld was caught up in the struggle between Jansenists and Jesuits for control of the French Church. After suffering numerous indignities but seeming to enjoy controversy, he finally left France and settled in Brussels where he spent the remainder of his life after 1682, writing against the Jesuits and in defense of Jansenism. His 320 works now collected in 43 volumes stand as an eloquent testimony of his intellectual vigor and reforming zeal.