Cornelius Jansen was a Dutch theologian born in 1585, known for founding the theological movement called Jansenism. He emphasized the importance of divine grace and the necessity of moral rigor in Christian life. His most notable work, Augustinus, was published posthumously in 1638 and argued against the prevailing views of Jesuit theology. Jansen's ideas sparked significant controversy within the Catholic Church, leading to conflicts with the Jesuits and other theologians. His teachings influenced various religious groups and contributed to debates on free will and grace. Jansen died in 1638, but his legacy continues to be discussed in theological circles.