St. Thomas Aquinas: Faith, Reason, and the Five Ways to God
Faith and Reason
According to St. Thomas Aquinas, there is only one truth, originating from God. He distinguishes between faith, based on divine revelation and attained through grace, and reason, achieved through human intellect. While distinct, faith and reason intersect on common ground, with reason subject to and complemented by faith.
St. Thomas identifies two types of propositions:
- Truths demonstrable only through reason (preambles of faith), such as God’s existence, the soul’s immortality, and the universe’s origin.
- Truths accessible solely through faith, not demonstrable by reason or sensory experience.
Creationism and Metaphysics
Christian metaphysics, according to St. Thomas, posits creation as a free and rational act of divine will, marked by contingency—meaning it could have been otherwise. This highlights the distinction between a thing’s essence (what it is) and its existence (that it is). Aquinas distinguishes essence and existence through the act-potency theory, where a substance is in potency relative to being, which is an act. God, the efficient cause, exercises causality eminently in creation, producing being ex nihilo—from utter nothingness—not from pre-existing matter.
Created Beings
St. Thomas distinguishes between immaterial substances (angels) and composite substances (material beings). He uses hylomorphic theory (matter and form) to explain material beings and the act-potency concepts to explain change. Act represents the full presence of a being’s features, while potency is the capacity for transformation (active potency) or to become something (passive potency).
The Existence of God
St. Thomas believes God’s existence requires proof, not being self-evident to reason, even with a clear understanding of the divine essence. His demonstrations start with sensory experience of created things, using the concept of God as a perfect being, both outside and inside the mind. He presents five ways to prove God’s existence, based on an epistemological foundation (Aristotle’s empirical theory of knowledge) and an ontological foundation (the principle of efficient causality).
The Five Ways
Each of the five ways follows a similar structure:
- A starting point based on sensory experience.
- Application of the principle of causality.
- Rejection of an infinite regress in causal series.
- Conclusion of a First Cause (God), possessing attributes of a perfect being.
1. Motion:
Sensory experience verifies motion. Everything that moves is moved by another. An infinite regress of movers is impossible, leading to a First Unmoved Mover.
2. Efficient Cause:
Sensory experience verifies causation. Every cause is caused by another. An infinite regress of causes is impossible, leading to a First Efficient Cause.
3. Contingency:
Sensory experience verifies the contingency of beings. Contingent beings cannot have always existed and must be caused by a necessary being. An infinite regress of necessary beings is impossible, leading to a single Necessary Being.
4. Degrees of Perfection:
Sensory experience verifies varying degrees of perfection. Things are judged as more or less perfect based on their proximity to a most perfect being. This gradation implies both participation and causation. An infinite regress of participants is impossible, leading to a Perfect Being.
5. Teleology (Purpose):
Sensory experience verifies order in beings. Things act for an end, not randomly. This order implies an intelligent being directing things towards their purpose.