JANSEN, CORNELIUS (1585-1638), bishop of Ypres, and father of the religious revival known as Jansenism (q.v.), was born of humble Catholic parentage at Accoy in the province of Utrecht on Oct. 28, 1585. In 1602 he entered the university of Louvain, then in the throes of a violent conflict between the Jesuit, or scholastic, party and the Augustinians, followers of Michael Baius. Jansen joined the latter party. He made a mo mentous friendship with a like-minded fellow-student, Du Vergier de Hauranne, afterwards abbot of Saint Cyran. After taking his degree he went to Paris, partly to recruit his health by a change of scene, partly to study Greek. Eventually he joined Du Vergier at his country home near Bayonne, and spent some years teach ing at the bishop's college. His spare time was spent in studying the early Fathers with Du Vergier, and laying plans for a refor mation of the Church. In 1616 he returned to Louvain, to take charge of the college of St. Pulcheria, a hostel for Dutch students of theology. Pupils found him a somewhat choleric and exacting master and academic society a great recluse. He took part in the university's resistance to the Jesuits, who had established a theological school of their own in Louvain, which was a formidable rival to the official faculty of divinity. Jansen was sent twice to Madrid, in 1624 and 1626; the second time he narrowly escaped the Inquisition. He warmly supported the Catholic missionary bishop of Holland, Rovenius, in his contests with the Jesuits. He also crossed swords more than once with the Dutch Presby terian champion, Voetius, still remembered for his attacks on Descartes.
Antipathy to the Jesuits brought Jansen no nearer Protestant ism ; he desired to prove to them that Catholics could interpret the Bible in a manner quite as mystical and pietistic as theirs. This became the great object of his lectures, when he was ap pointed regius professor of scriptural interpretation at Louvain in 163o. Still more was it the object of his Augustinus, a bulky treatise on the theology of St. Augustine, barely finished at the time of his death. Its preparation had been his chief occupation ever since he went back to Louvain. But Jansen, as he said, did not mean to be a school-pedant all his life; and there were moments when he dreamed political dreams. He looked forward to a time when Belgium should throw off the Spanish yoke and become an independent Catholic republic on the model of Protest ant Holland. These ideas became known to his Spanish rulers, and to assuage them he wrote a philippic called the Mars gallicus (1635), a violent attack on French ambitions generally, and on Richelieu's indifference to international Catholic interests in par ticular. The Mars gallicus did not help Jansen's friends in France, but it appeased the wrath of Madrid against Jansen, and in 1636 he was appointed bishop of Ypres. He died on May 6, 1638; the Augustinus, the book of his life, was published posthumously in 1640.
Full details as to Jansen's career will be found in Reuchlin's Geschichte von Port Royal (Hamburg, 1839), vol i. See also Jansinius by the Abbes Callawaert and Nols (Louvain, 1893).