Thomas Aquinas’s Philosophy: Exploring Existence, Ethics, and Knowledge
Thomas Aquinas’s Proofs for God’s Existence
The Five Ways
In theology, God is the undisputed starting point. However, from a philosophical perspective, Aquinas believed it necessary to prove God’s existence because the idea is not innate. He argued that God’s existence cannot be demonstrated from His definition alone, as there’s no single definition for Him. Aquinas asserted that we can only know what is perceived through the senses, which excludes the divine essence.
To prove God’s existence, Aquinas developed demonstrations called the ‘Five Ways’. These arguments follow a consistent structure:
- Start with evidence from the senses.
- Apply an accepted metaphysical principle (e.g., causality).
- Show that denying God’s existence leads to absurd conclusions when applying the principle.
- Conclude that God must exist.
The Five Ways are:
- The Argument from Motion: Everything that moves is moved by something else. This chain of movers cannot go on infinitely, so there must be a first unmoved mover, which is God.
- The Argument from Efficient Cause: Every effect has a cause. This chain of causes cannot go on infinitely, so there must be a first uncaused cause, which is God.
- The Argument from Necessary Being: Contingent beings (those that could have not existed) depend on a necessary being for their existence. This necessary being is God.
- The Argument from Gradation: We observe degrees of perfection in things (e.g., goodness, truth). There must be a most perfect being that is the source of all perfections, which is God.
- The Argument from Design: The universe exhibits order and purpose. This implies an intelligent designer, which is God.
These arguments collectively lead to the conclusion that God exists.
Ethics: Natural Law and Positive Law
The Pursuit of Happiness and Virtue
Aquinas’s ethics is eudemonistic, aiming at happiness, which he equates with perfection and excellence. He identifies two types of virtues: theoretical and ethical. The contemplative path develops theoretical virtues, leading to happiness through the contemplation of God. This requires God’s grace to enlighten the soul. The active path develops moral virtues through habitual good actions, guided by reason.
Natural Law
When deliberating on moral issues, reason discovers natural law, which consists of basic principles embedded in human nature, such as “Do good and avoid evil.” Natural law originates from God and governs both natural objects and humans. It is an unwritten, universal, and unchanging law that all humans recognize, though they may violate it. The philosophical school that affirms the existence of natural laws is known as natural law theory.
Theory of Knowledge: Reason and Faith
Two Paths to Truth
Aquinas believed that truth is singular but can be attained through two paths: reason and faith. Reason derives knowledge from sensory data, while faith relies on divine revelation. Reason and faith are distinct yet complementary.
Truths of Faith and Truths of Reason
Truths of faith, or revealed truths, transcend human reason and are studied by theology. They cannot be proven rationally and are accepted without question because they come from God. Truths of reason, or philosophical truths, can be understood by the human mind and are rationally demonstrable.
The Relationship Between Reason and Faith
Philosophy can illuminate some articles of faith but doesn’t replace faith; it serves as a preamble. Aquinas argued that we cannot know and have faith in the same thing simultaneously because faith involves uncertainty. Reason and faith work together to reach revealed truth. Truth is one, and if philosophy contradicts faith, reason is in error. Therefore, Aquinas emphasized the importance of understanding in order to believe, rather than believing in order to understand.
Knowledge Acquisition
Aquinas’s philosophy is grounded in sensory data. His empiricism led him to reject the existence of innate ideas. He believed the mind is a blank slate (tabula rasa) and all ideas are acquired through the senses or experience. He distinguished between two types of knowledge: sensible and abstract. Sensible knowledge is gained through the senses and imagination, forming a mental image called a ‘phantasm’. Abstract knowledge involves the intellect performing two functions: abstraction (identifying common aspects across objects) and the formation of universal concepts based on information from the passive intellect.
Humans can only directly know the sensible world. Although God is beyond the senses, we can have indirect knowledge of Him.
Anthropology: The Hylomorphic View
The Human Being as a Unity of Body and Soul
Aquinas’s conception of the human being follows Aristotle’s hylomorphic theory. Humans are understood as a substantial unity composed of matter (the body) and form (the soul). There are three types of souls: rational (human), sensitive (animal), and vegetative (plant). Aquinas believed the soul, particularly the rational part called the active intellect (responsible for abstraction), is immortal.