JANSEN (Cornelius), bishop of Ypres, one of the most learned divines of the 17th century, and principal of the sect called from his name Jansenists. He was born in Holland of Catholic parents, and studied at Louvain. Being sent to transact some business of consequence relating to the university, into Spain, the Catholic king, viewing with a jealous eye the intriguing policy of France, engaged him to write a book to expose the French to the pope as no good Catholics, since they made no scruple of forming alliances with Protestant states. Jansen performed this task in his Mars Gallicus; and was rewarded with a mitre, being promoted to the see of Ypres in 1635. He had, among other writings, before this, maintained a controversy against the Protestants upon the points of grace and predestination; but his Augustinus was the principal labour of his life, on which he spent above 20 years. See the next article.