Jansen, Cornelius (1585–1638), Dutch Roman Catholic theologian. In 1636 he was appointed bishop of Ypres, Belgium. In Augustinus (published posthumously, 1640), Jansen argued for a return on the part of Christians to the positions of St. Augustine on grace, free will, predestination, and salvation. Though counter to church doctrine, these ideas attracted many Catholic followers in France and the Low Countries. Early 18th-century papal bulls discredited Jansenism, but in parts of the Netherlands Jansenists still have churches.
See also: Theology.