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Christian Thinkers 101: A Crash Course on St. Anselm

Can faith and reason be compatible? Does reason support the truth-claims of Christianity? Many people today believe in a false dichotomy that forces faith and reason into separate categories—but thinkers like St. Anselm, a medieval Italian, have offered compelling arguments for integrating faith and reason. St. Anselm’s ontological argument for God’s existence was a significant, though controversial, contribution that still impacts Christian apologetics. Here’s your crash course on the life and accomplishments of St. Anselm—and why he matters today.

Who Was St. Anselm?

After joining the Benedictine order as a monk, St. Anselm (1033–1109) became a high-ranking ecclesiastical figure serving in church leadership in France and England. Ultimately, he became archbishop of Canterbury. Throughout his adult life, St. Anselm sought to reform the church and monastic life. He was a major Catholic theologian and philosopher and made important contributions to Christian doctrine, philosophical theology, and apologetics. Though an Augustinian in his basic approach to theology and philosophy, St. Anselm contributed his own unique and powerful insights to Christian thought. He was also known for his rich devotional life; some of his prayers and meditations have been preserved in his writings.

What Did St. Anselm Write?

Among several works, St. Anselm’s two most important apologetics-related books are Cur Deus Homo (Why the God-Man?) and Proslogion (Discourse). In Cur Deus Homo, he explains and defends why Jesus Christ the Savior must be both God and man (a single person who has both a divine and a human nature) in order to reconcile a holy God with sinful humanity. In Proslogion, St. Anselm tackles the relationship between faith and reason and the arguments for the existence of God.

What Did St. Anselm Believe?

Perhaps St. Anselm’s three most important ideas or arguments for the God of Christian theism are the following:

  1. Once a person becomes a believer via divine grace, the Christian then uses his or her mind to uncover the necessary reasons behind the historic Christian faith. Thus, Anselm’s approach to reflection begins in faith but then achieves understanding through reason. Ultimately faith and reason are understood to be compatible.
  2. The biblical God is the greatest conceivable being (a being “than which none greater can be conceived”) and thus God’s existence may be known through the rational reflection of God’s perfect nature. St. Anselm’s ontological argument is understood as a pure a priori rational argument for God’s existence and is considered the most controversial and contested of all the so-called traditional proofs for God.
  3. St. Anselm’s Satisfaction Theory of Atonement says that humanity’s fall into sin injured God’s honor. Therefore, humankind must render satisfaction to a righteous God, but only God can truly make amends—and He did, through Christ’s sacrifice.

Why Does St. Anselm Matter Today?

Philosophers have been divided over the viability of St. Anselm’s ontological argument.1 However, contemporary Christian philosopher Alvin Plantinga has defended a form of St. Anselm’s ontological argument, reinforcing that it shows belief in God is rational.2 So philosophers, both Christian and non-Christian, are reflecting upon St. Anselm’s ideas almost 1,000 years after his death.

St. Anselm of Canterbury is revered as a doctor of the Catholic Church and has been called the greatest Christian thinker between St. Augustine and St. Thomas Aquinas. He is also known as the father of scholasticism for his major contributions to medieval theology and philosophy. He is known for his ability to successfully combine the challenging roles of church leader and scholar.

St. Anselm has also influenced evangelical protestants. For when evangelicals suggest that faith and reason are compatible or that unbelief is unreasonable, they are affirming some of St. Anselm’s ideas.

Other articles in the Christian Thinkers 101 series: St. Augustine; C. S. Lewis; Blaise Pascal; St. Athanasius; St. Thomas Aquinas; Jonathan Edwards; Søren Kierkegaard; St. Bonaventure; Martin Luther; John Calvin; Irenaeus; Tertullian; St. Basil; St. Jerome; Justin Martyr; Walter Martin; Ronald Nash; Mortimer Adler

Reflections: Your Turn

St. Anselm suggested that the person who has faith should seek understanding. How do you view faith’s relationship to reason? Visit Reflections on WordPress to comment with your response.


  • See The Prayers and Meditations of St Anselm with the Proslogion by St. Anselm.
  • For an analysis of St. Anselm’s life and thought, see A History of Apologetics by Avery Dulles.
  1. J. P. Moreland, Chad Meister, and Khaldoun Sweis, eds., “A Modal Version of the Ontological Argument” and “Lowe on ‘The Ontological Argument,’” in Debating Christian Theism (New York: Oxford University Press, 2013), 61–83.
  2. Alvin Plantinga, God, Freedom, and Evil (Grand Rapids: Eerdmans, 1974), 85–111.