Saint Thomas Aquinas: Faith, Reason, and God's Existence

Saint Thomas Aquinas: Philosophy and Theology

Philosophical truths are known as natural truths. Revealed truths are those of faith (theology).

• Complementarity between Faith and Reason: There can be no contradictions between the claims of natural theology and dogmatic theology. If deductions are correct, philosophy can achieve the same truths as revelation. Aquinas denies the theory of double truth attributed to Averroes, since natural theology and dogmatic theology employ different procedures to arrive at the same conclusion.
• Philosophy as a Preamble to Faith: Philosophy makes some articles of faith understandable, but it does not replace them; rather, it acts as a preamble. For Saint Thomas, one cannot simultaneously know and have faith, because faith implies uncertainty.
• Theological Truths Guide Philosophy: Theology does not dictate the procedures that philosophy should use, but revealed truths are a reference point that can distinguish between sound philosophical reasoning and erroneous conclusions.
• Ultimate Truth Unattainable for Philosophy: Theological philosophy cannot reveal all the mysteries of religion.
• Philosophy as a Methodological Tool for Theology: Philosophy also deals with other issues that do not directly affect theology but provides methodological tools that theology can employ.

Proofs for God's Existence: The Five Ways

Saint Thomas Aquinas considered it necessary to demonstrate the existence of God, asserting that this idea is not self-evident. Thomas Aquinas rejected the notion that God's existence could be demonstrated from His definition, as no such definition exists.

• The Five Ways: To prove the existence of God, Thomas Aquinas proposed five demonstrations, which he called ways. All ways follow the same structure:
  • Starts from an evident fact of experience.
  • Applies an accepted physical or metaphysical principle.
  • If one denies the existence of God, applying the principle leads to absurd metaphysical conclusions.
  • The conclusion is that God exists.

The Way of Motion (First Mover)

Things are in motion, and everything that moves needs a mover. This mover or cause of motion has been set in motion by another mover. As there cannot be an infinite sequence of movers, one must conclude that there is a first mover that moves and is not itself moved. This first mover is God.

The Way of Efficient Cause (First Cause)

All existing beings are caused by an efficient cause that created them. Since nothing can generate itself, it always requires an external cause. However, it is absurd to think that there is an infinite sequence of causes. It is therefore necessary to conclude that there exists a first cause that is itself uncaused. This uncaused cause is God.

The Way of Contingency (Necessary Being)

All that surrounds us exists but could also not exist; it is contingent. Each of the beings that inhabit the cosmos exists, but could cease to exist. This means that everything around us is contingent. Contingent beings derive from other contingent beings, but an endless chain of generations makes no sense, as nothing can come from nothing. Therefore, there must be a divine creator, a necessary being. This necessary being is God.

The Way of Degrees of Perfection (Supreme Good)

All people are capable of judging facts and actions and qualifying them as better or worse. This is possible because there is a supreme good. This ultimate and highest good is God.

The Way of Teleology (Governance of the World)

In the world, all that happens is directed towards an end or purpose. Since natural objects tend towards an end, that end must have been imposed by a divine mind.

Metaphysics: Essence and Existence

One of Aquinas's major contributions relates to the distinction between essence and existence.

Aquinas defines essence and existence as follows:

• Essence:
  • It is what defines an entity.
  • It is composed of matter and form.
  • It is what all individuals of the same species share, both in terms of form and matter.
  • It is identified with the Aristotelian potency (potentiality) because it is something that can exist.
• Existence:
  • It is that by which the essence exists.
  • It is identified with the Aristotelian act (actuality) as it is something that actualizes the essence.