Introduction to St. Thomas Aquinas
St. Thomas Aquinas (1225–1274) was a Dominican friar, priest, and influential philosopher and theologian in the tradition of scholasticism. His work represents the peak of Medieval philosophy, primarily through his monumental synthesis of Aristotelian logic and science with Christian revelation. Aquinas argued that reason and faith are not contradictory but complementary, both originating from the same divine source.
The Synthesis of Faith and Reason
The central project of Thomism is the demonstration that human reason, when properly exercised, leads to truths that are consistent with divine revelation. Aquinas distinguished between “natural theology,” which can be known through the light of natural reason (such as the existence of God), and “revealed theology,” which requires faith and divine disclosure (such as the doctrine of the Trinity).
The Five Ways (Quinque Viae)
In his Summa Theologica, Aquinas proposed five logical arguments for the existence of God, known as the Quinque Viae:
- The Argument from Motion: Everything that moves is moved by something else. This chain cannot go back to infinity; therefore, there must be a First Mover, which is God.
- The Argument from Efficient Cause: Nothing can be the efficient cause of itself. To avoid an infinite regress of causes, there must be a First Cause, which is God.
- The Argument from Possibility and Necessity: Contingent beings (things that could not have existed) require a Necessary Being (one that must exist) to bring them into existence.
- The Argument from Gradation: We perceive degrees of perfection (goodness, truth, beauty). These degrees imply a standard of absolute perfection, which is God.
- The Argument from Design (Teleology): Non-intelligent things act toward an end or purpose. This suggests they are directed by an intelligent designer, which is God.
Thomistic Metaphysics: Act and Potency
Aquinas adopted Aristotle’s concepts of actuality (entelcheia) and potentiality (dynamis) to explain change and the nature of being. For Aquinas, God is Actus Purus—pure actuality without any potentiality. All other beings are a composition of essence (what they are) and existence (that they are). In God alone, essence and existence are identical.
Ethics and Natural Law
Aquinas’s ethical theory is grounded in his concept of Law, which he divided into four categories:
- Eternal Law: The divine wisdom of God which oversees the universe.
- Natural Law: The participation of rational creatures in the eternal law through reason. It dictates that “good is to be done and evil avoided.”
- Human Law: Specific applications of natural law formulated by human societies (e.g., traffic laws).
- Divine Law: The law revealed in Scripture (e.g., the Ten Commandments).
Natural law provides a universal moral framework accessible to all humans, regardless of their religious beliefs, based on the pursuit of basic human goods: life, procreation, knowledge, and social living.
The Theory of Knowledge (Epistemology)
Aquinas was an empiricist in the Aristotelian sense, famously stating: Nihil est in intellectu quod non sit prius in sensu (Nothing is in the intellect which was not first in the senses). He rejected the Platonic idea of innate knowledge, arguing that the human mind abstracts universal concepts from particular sensory experiences through the “active intellect.”
Political Philosophy
Aquinas viewed the state as a natural institution necessary for the common good. While he believed the church was superior in spiritual matters, he argued that the temporal ruler should govern in accordance with the common good and justice. If a law contradicts natural law, it is a “perversion of law” and does not bind the conscience.
Legacy and Influence
Aquinas’s influence on Western thought is immeasurable. Thomism became the official philosophy of the Catholic Church, but its impact extends far beyond religious thought, influencing the development of modern science, international law, and human rights theory. His commitment to rigorous logical analysis and the reconcilability of different domains of knowledge remains a hallmark of the intellectual tradition.
Conclusion
The Thomistic project remains a vital branch of contemporary philosophy. Whether in metaphysics, ethics, or the philosophy of law, Aquinas’s insistence on the harmony of reason and revelation continues to challenge and inform modern inquiries into the nature of reality and the human condition.