Anselm was born at Aosta, in the Burgundian Alps, in 1033 or 1034. After a wandering youth he crossed into Normandy to study under Lanfranc at the abbey of Bec, took the habit there, and rose to be prior and then abbot, making Bec one of the intellectual centers of Europe. At Bec he wrote the works that made his name: the Monologion, which argues from the degrees of goodness in things to a single supreme good, and the Proslogion, which compresses everything into one famous stroke, the ontological argument, reasoning that that than which nothing greater can be conceived cannot exist in the understanding alone. The argument has been attacked from Anselm's own lifetime to the present, defended by thinkers from Descartes to modern modal logicians, and never quite killed; it remains the most discussed single argument in philosophical theology.
His program he stated in a phrase that named medieval thought's whole method: fides quaerens intellectum, faith seeking understanding. In 1093 he was dragged, genuinely protesting, to the see of Canterbury, and spent much of his episcopate in exile, contesting the rights of the church against Kings William Rufus and Henry I in the investiture quarrels. He died at Canterbury in 1109, was canonized, and in 1720 was declared a Doctor of the Church.