St. Thomas Aquinas: Philosophy, Theology, and the Five Ways
St. Thomas Aquinas: A Synthesis of Philosophy and Theology
St. Thomas Aquinas made significant contributions to philosophy and theology by synthesizing previous philosophical thought. His greatest achievement was incorporating ideas from Aristotle, Christian, Jewish, and Muslim thinkers. His work is essential reading for philosophers from the Middle Ages to the present. Aquinas dedicated his life to religious service as a Dominican monk and to tireless study and teaching.
The Existence of God: Natural Knowledge and Reason
According to St. Thomas, humans possess a natural understanding of God’s existence, attainable through reason and logic, even without Christian revelation or faith. Reason, when applied logically and scientifically, can lead to certainty about God’s existence, as well as the soul’s immortality and spirituality. These assertions are known as the preambles of faith. Reason precedes faith, and philosophy precedes theology, diverging from the Augustinian belief that faith precedes understanding (credo ut intelligam).
Aquinas rejects Anselm’s ontological argument, which posits that we can know God directly through consciousness. Instead, Aquinas’s argument relies on evidence and the metaphysical distinction between essence and existence. This distinction, a novel concept in philosophy, defines essence as the set of properties that constitute a being, answering the question, “What is it?” Existence, on the other hand, is the actual realization of that essence, beginning at its inception. In God, this distinction does not exist because God’s essence is full existence, existing by itself. God’s existence is eternal and the cause of all other beings.
Aquinas argues that the proposition “God exists” is self-evident, but not to us, as limited beings. A thesis or statement is self-evident when the predicate is included in the concept of the subject, forming part of its core properties. While God’s existence is self-evident in this way, it needs to be demonstrated a posteriori, through things more accessible to us, even if those things are less obvious.
The Five Ways: Demonstrating God’s Existence
Aquinas favors an a posteriori proof, moving from effects to causes, ultimately leading to the acceptance of a First Cause, which he calls God. St. Thomas presents a strict demonstration, known as the five ways or roads, leading to the affirmation of God’s existence. These pathways share a common structure of causality: every effect has a cause, and an infinite chain of causes is impossible. Therefore, we must conclude the existence of an uncaused First Cause, or Causa Sui, which is God.
These five ways, and all of St. Thomas’s thought, summarize earlier philosophers, but their originality lies in their structure for demonstrating God’s existence. God’s main attribute is Aseidad: God is full existence, where essence and existence are identical. God is the Causa Sui, the foundation of all other beings, including humans.
Ethics, Politics, and Natural Law
In ethics, Aquinas follows Aristotle’s eudaimonistic guidance: the end of moral actions is the pursuit of happiness (eudaimonia). However, this happiness cannot consist of possessing anything created; it can only be found in God through the beatific vision. An act is good if it leads to that ultimate goal and bad if it deviates from it. To distinguish between good and bad, we must rely on their agreement with the natural moral law, which is participation in the created from the eternal law of God. Thomas was the initiator of natural law.
Natural law is the precedent of what we now call human rights. In politics, Aquinas states that the authority of rulers comes from God, but the leader should have consultants representing the people. The best form of government is a mixture of monarchy, aristocracy, and democracy. In any event, he recognizes the people’s right to rebel against rulers when they are corrupt and have not sought the ultimate end state, which is the common good. Positive law is an ordinance of reason, directed to the common good, issued by the competent authority, and sufficiently promulgated. This definition of positive law is notable for its accuracy and initiated a major issue in later philosophy: the harmony between morality and legality.