Aquinas’ Philosophical Theology: Proving God’s Existence

Religious and Philosophical Theology

Aquinas distinguishes between religious and philosophical theology. Philosophical theology uses reason to explore religious truths, while religious theology relies on faith. Statements like “God died and rose again” are accepted through belief, not proof. Following Aristotle, Aquinas argues that concepts like God’s existence can be examined through reason, leading to philosophical theology.

The difference lies not in the object (God) but in the approach: reason or faith. Natural theology serves as an introduction to theology within Catholicism.

Demonstrating God’s Existence

Aquinas addresses God’s existence with a two-part response:

• God’s existence is not self-evident and requires demonstration.
• Proof must proceed from the known world to the unknown God.

He rejects arguments that attempt to prove God’s existence from the concept of God as perfection. Aquinas believes this approach reverses the order from the ideal to the real. While he acknowledges that God’s essence implies existence, this does not prove God’s existence. Kant later argued that existence is not merely perfection but a matter of experience.

Structure of the Ways

Aquinas’ arguments for God’s existence share a common structure:

• They begin with a fact in the world (motion, causality, birth and death, degrees of perfection, natural order).
• These facts require the principle of causality for explanation.
• Infinite regression is impossible, necessitating a first cause.
• This first cause is identified as God.

Considerations

Aquinas views the world as a real object, while Kant sees it as an idea. Aquinas considers the causal relationship as real, while others like Hume and Kant question it. The problem is not just explaining things but finding a first cause.

Aquinas’ approach is vertical, with events dependent on God. He identifies the end of each argument with God, though this connection is not immediately obvious. The concept of cause is later justified as God.

Exposure Pathways

The Argument from Motion

Based on Aristotle, this argument starts with the premise that “everything that moves is moved by another.” This leads to God as the prime mover. Aquinas distinguishes between act and potential. Motion is the change from potential to act, requiring a first mover, which is God. This applies to changes in place, quantity, quality, and being.

The engine of the world is the source of life and activity. Aristotle and Aquinas move from the physical cause of motion to the metaphysics of God. Galileo, however, focused on the causes of changes in motion within physics.