Anselm (c. 1033–1109) was a Benedictine monk and Archbishop of Canterbury, the first great medieval theologian whose principle of "faith seeking understanding" (credo ut intelligam) fundamentally shaped scholasticism. He formulated the satisfaction theory of atonement and the ontological argument. A defender of ecclesiastical independence against royal authority, he endured voluntary exile twice rather than compromise the Church's liberty. His vast literary corpus and sincere ascetic spirituality combined intellectual rigor with pastoral dedication.

Anselm's theological legacy rests on two pillars: the ontological argument for God's existence (Proslogion, 1077–78) and the satisfaction theory of the atonement (Cur Deus Homo, 1098). The ontological argument — that God is 'that than which nothing greater can be thought,' and that such a being must exist in reality as well as in the mind — has generated continuous philosophical debate from Gaunilo's contemporary rebuttal through Kant's critique to Plantinga's modal reformulation. Cur Deus Homo reframed atonement theology by arguing that only a God-man could offer the satisfaction owed to divine honor by human sin, displacing the earlier ransom theory that had dominated patristic thought. Both works exemplify Anselm's method of 'faith seeking understanding' (fides quaerens intellectum) — not proving faith by reason alone, but pressing reason into service within the life of faith. His monastic writings, especially the Prayers and Meditations, reveal a devotional warmth that balances his intellectual rigor. The prayers to the Virgin Mary and to St. Paul anticipate later medieval affective piety while remaining grounded in scriptural imagery. Anselm was canonized in 1494 and declared a Doctor of the Church in 1720. His influence runs through Aquinas (who adopted and modified the satisfaction theory), Descartes (who revived the ontological argument), Barth (who devoted his first major work to Anselm's theological method), and contemporary analytic philosophy of religion.

Anselm was born in Aosta in the foothills of the Alpine region and trained at the monastery of Bec in Normandy under the celebrated Lanfranc. He became prior (1063) and then abbot (1078) of Bec, earning a reputation across Europe for his theological acumen and monastic reformism. In 1093, King William II appointed him Archbishop of Canterbury, though he accepted with reluctance. His tenure was marked by fierce disputes over the investiture controversy and Church-State authority. Anselm insisted that the Church's independence from secular rulers was non-negotiable; he resisted both William Rufus and his successor Henry I, going into voluntary exile (1097–1100 and 1103–1106) rather than compromise ecclesiastical liberty. During his final years at Canterbury, he maintained extraordinary intellectual vigor, debating theology and revising his works until his death. Eadmer, his companion and secretary, records that Anselm continued deep theological discussion on his deathbed. His life embodied the conviction that reason and faith must work together in seeking God's truth.

• Doctor
• Bishop