St. Thomas Aquinas: Reason, Faith, Metaphysics, and God
St. Thomas Aquinas: Valuing Reason and Faith
According to St. Thomas Aquinas, philosophy is the “handmaid of theology,” but that does not take away its dignity or autonomy. Faith only informs from the outside, so it cannot contradict truth (which would contradict dogma), because truth can only be one. Philosophy helps the theologian to demonstrate some basic truths related to the Christian faith’s proposals (the so-called “preambles of faith,” e.g., the existence of God or the immortality of the soul) and to clarify truths known only by revelation (“articles of faith,” such as the Trinity or the incarnation of God).
Metaphysics
St. Thomas Aquinas accepts the Aristotelian conception of ontology as the “science of being qua being” and his theory of causes or categories. He also introduces Aristotelian hylomorphism into Scholasticism and considers that the principle of individuation is matter, regarded as a divisible quantity. However, Thomistic metaphysics is especially characterized by its theistic nature, emphasizing the distinction between the finite being and finite beings through his doctrine of the analogy of being and the distinction between essence and existence in finite beings and their identity in God. On the question of universals, he advocates a moderate realism: before things exist, the universal exists only in the mind of God; after creation, it is in things and can then be abstracted from them by the human mind.
God
At the beginning of his most important work, the Summa Theologica, St. Thomas Aquinas raises three questions: Is the existence of God obvious? Can it be demonstrated? How? To the first question, he answers that it is self-evident in itself, but not for us, because we do not fully understand God’s essence. As for the second, he maintains that it can be demonstrated, but not as Saint Anselm tried to do with what Kant called the “ontological argument,” because that only proves God’s existence in the understanding. St. Thomas Aquinas believes that God’s existence can only be demonstrated from its effects.
In the Summa Theologica, Part I, Question 2, Article 3, he presents his famous five ways. All have the same structure, consisting of four phases:
- Based on the finding of a fact of the senses (1st motion, 2nd efficient causes, 3rd the contingent, 4th degrees of perfection, and 5th the order of the world).
- Apply the principle of causality.
- Note the impossibility of extending the series of causes to infinity.
- Conclude by affirming the existence of a being to which all refer as God.
After proving God’s existence, St. Thomas Aquinas studies God’s essence or nature. He says that God is simple, one, infinite, perfect, and immutable. God’s operational attributes are creation, providence, concurrence (acting as the first cause of secondary causes), and conservation in the existence of creation.
Anthropology
St. Thomas Aquinas maintains the Aristotelian hylomorphic conception according to which man is a composite of body and soul. Unlike Aristotle, however, he considers that the soul is immortal and is directly created by God. The human soul is the immaterial principle of intellectual activity, so it can survive even though the body to which it is attached dies. The soul is the substantial form of man and carries out its activities through five types of powers or faculties:
- Vegetative powers
- Sensory powers (the five external senses and the four internal ones: common sense, imagination, sensory memory, and the estimative power)
- The sensitive appetite
- The locomotive powers
- Intellective powers (understanding and will), the latter being exclusive to humans