Is it possible to prove the existence of God?

SAINT THOMAS Aquinas by Fra Bartolomeo

This modern question has a medieval backwater through which we must wade to consider a coherent response. Ancient peoples rarely questioned the existence of a divine being (or beings), although they often wondered whether the Deity was rooting for or against humanity in any given circumstance. Even as late as the Middle Ages, the theologians who posited arguments for God's existence didn't personally question the matter: They were merely tying up loose philosophical ends. Eleventh-century Saint Anselm was first, offering an ontological proof—that is, a proof based on the meaning of the term "God": If we can imagine the greatest reality which is God, and a real thing is greater than an imaginary thing, then God must be that real and not only imaginary greatness.

Two centuries later Saint Thomas Aquinas raised five proofs for God's existence— motion, causality, possibility and necessity, gradations, and governance—each of which follows a similar argument. Take motion, for example: When something moves, there is a mover that causes the motion. God is the First Mover that set everything in motion. Or consider causation: Actions have consequences, but somewhere there is a Cause which originally caused everything else. Or gradation: A good thing points to a better, which presumes a best. God is that which is Best.

Arguments like these are philosophically neat, but they didn't withstand the keen rational edge of the 18th-century Enlightenment gang. In Philosophy 101 courses every student learns how David Hume and Immanuel Kant discovered flaws in the medieval proofs. Kant, at least, saw the idea of God as necessary for morality to be possible. In the same period William Paley argued for God's existence from the intricate design of the world, which presumes a grand Designer the way a watch found on a beach presumes that someone left it there because it didn't just spring from the sand. This proof isn't really much distinct from the Aquinas approach.

The Bible offers no proofs for God's existence. As a product of revelation, it seeks to tell us about God's nature, not to prove that God is real. Revelation is abundantly useful for people of faith and quite problematic to people without it. So when the church says that the Creator can be known from creation, that is a statement of how God can be understood by those who seeking understanding. It doesn't suggest how God can be rationally proven to those who are skeptical of the religious enterprise altogether.

Scripture
• Mark 10:51-52; 11:22-24; Luke 11:9-13; 2 Corinthians 5:7

Online
• Thomas Aquinas, "Reasons in Proof of the Existence of God" from the Summa Theologia

Books
• An Introduction to Catholic Theology by Richard Lennan (Paulist Press)
• Spirituality Seeking Theology by Roger Haight (Orbis Books, 2014)