Thomas Aquinas: Faith, Metaphysics, Physics, Anthropology

Saint Thomas Aquinas

1. The Problem of Reason and Faith

Faith and reason are two faculties that are at the same level and have the same value, each dealing with its own domain.

• The truths we know by faith: we know them through revelation.
• The truths we know by reason: we know them by reasoning.

There is common ground that Thomas Aquinas called the preambles of faith. In this common ground, if faith and reason come into conflict, the more authoritative is faith. If philosophy and theology conflict in this field, theology is more important. The common ground is developable.

2. Metaphysics

Thomas Aquinas has a monistic view of reality: there is one natural world. In every natural thing there is something that remains; that which remains is in this world—there are not two worlds.

2.1 Theory of Substance and Accident

In every natural thing we can distinguish a substance and some accidents. The substance is what a thing is by itself. The accident is something that exists in another.

In turn, the substance is composed according to the hylomorphic theory of matter and form (essence).

"What the substance is, it has by itself. The accident is something that exists in another."

2.2 Theory of Act and Potency

Everything in this world is simultaneously in two states: in act and in potency. A distinction can be made between events (what is now and what is now not) and powers (the ability to be and being).

2.3 Analogy of Being

The analogy of being means that being is predicated similarly across different categories. Predication is not purely univocal; being is similar — i.e., partly the same and partly different.

2.4 Essence and Existence

Essence: the set of characteristics that make something what it is and nothing else. Essence can be considered with respect to act (actuality) and potency (potentiality).

This happens in contingent beings, beings that can exist or not exist. Others are necessary, always there, pure act.

3. Physics

Hylomorphism theory. Physics studies natural things and, according to hylomorphism, every natural element consists of matter and form. There is no matter without form, nor form without matter. What defines a natural thing is that it is subject to movement (a transition from potency to act).

Two basic types of motion:

• Substantial: it affects the substance. Two kinds: birth and death.
• Accidental: it affects accidents.

Three types of accidental movement: quantitative change, locative change (change of place), and qualitative change (alteration).

4. Anthropology

4.1 Substantial Unity of the Human Being

Like Aristotle, Thomas has a monistic view of human beings. He posits the substantial unity of a material principle (body) and a formal principle (soul): there is no body without a soul and no soul without a body. The soul is subsistent; when the body disappears, the soul remains because it is a subsistent, a substantial principle capable of existing in a way distinct from the body.

For Aquinas, the soul is immortal: it is a remaining element and therefore eternal.

It has three faculties:

• Vegetative — in common with all living things.
• Sensitive — in common with animals.
• Intellective — characteristic of the human.