Thomas Aquinas’ Philosophy: Key Principles and Insights
Routes
Proofs for God’s Existence
This section explores arguments for the existence of God, addressing two key questions:
Is it Necessary to Prove God’s Existence?
Ontologism argues that God’s existence is self-evident and requires no proof. However, Thomas Aquinas, drawing from Aristotelian thought, posits that God’s existence is self-evident only to divine intelligence, not to human understanding.
Is it Possible to Prove God’s Existence?
Agnostics believe it’s impossible. Aquinas, however, argues that God’s existence can be rationally demonstrated through a priori and a posteriori reasoning. The a priori argument suggests that God, being perfect, must exist, as existence is a component of perfection. The a posteriori arguments, known as the Five Ways, derive from empirical observation.
The Five Ways
The Argument from Motion:
Everything that moves is moved by something else. This chain of movers cannot regress infinitely; there must be a First Mover, unmoved itself, which is God.
The Argument from Efficient Causes:
Everything has an efficient cause. This chain of causes cannot regress infinitely; there must be a First Cause, uncaused itself, which is God.
The Argument from Contingency:
Things exist contingently; they could exist or not exist. If everything were contingent, there would be a time when nothing existed, which would preclude the existence of anything now. Therefore, there must be a necessary being, which is God.
The Argument from Degrees of Perfection:
We observe degrees of perfection in things (goodness, truth, nobility). There must be a source of ultimate perfection, which is God.
The Argument from Teleology:
Natural bodies, lacking knowledge, act for an end. They must be directed by an intelligent being, which is God.
Anthropology
The Nature of Man
Man is created in God’s image and likeness. Aquinas’s hylemorphic theory posits that man is a substantial unity of body and soul. The soul, the vital principle, enables knowledge. There are three types of souls:
- Vegetative: Found in plants.
- Sensitive: Found in animals, enabling movement and sensation.
- Rational: Unique to humans, enabling thinking and understanding. Aquinas adds the will, which directs desire towards happiness.
Free will is the capacity to choose the means to achieve happiness. The soul’s simplicity and spirituality guarantee its immortality. The innate human desire for immortality further supports this.
Epistemology
The Theory of Knowledge
Knowledge is acquired through experience. Senses provide perceptions. The agent intellect abstracts universal concepts from these perceptions. The passive intellect stores these concepts.
Ethics
The Pursuit of Happiness
Ethics is teleological; all actions aim towards an ultimate end: happiness. Perfect happiness is the direct contemplation of God, achieved through blessedness. Blessedness requires both good deeds and divine grace. Two types of virtues exist:
- Intellectual Virtues: Enable proper reasoning.
- Moral Virtues: Guide character and choices.
Natural law, an innate principle to do good and avoid evil, informs moral action. Eternal law is God’s ordering of the universe towards the good.
Politics
The Organization of Society
Man is a social being, requiring community. Society is divided into:
- State: Aims for the common good.
- Church: Aims for the salvation of souls.
If positive laws conflict with natural moral law, rebellion against positive law is justified, as the Church’s authority stems from divine law.