Thomas Aquinas: The Medieval Philosopher
The luminary mind behind Europe's High Middle Ages.
Thomas Aquinas was one of the most brilliant minds of Western Europe in the Middle Ages. A devotee of Aristotle, he combined pagan philosophy with Catholic theology into an intellectual synthesis known as Scholasticism. Thomism, as his philosophy came to be called, dominated the universities of medieval Christendom for centuries, and reflects the most enduring achievements of Western thought from the High Middle Ages.
Eclecticism
Aquinas was a deeply eclectic thinker, masterfully weaving various intellectual sources into a single cohesive system. Thomas was a learned man. He was intimately familiar with the Classical tradition. The goal of his philosophical project was more than just baptizing Aristotle. He attempted to create his own comprehensive outlook on reality, rooted in Christian revelation but expressed through the finesse of Greco-Roman philosophy.
Thomas’ eclecticism came from his mentor, Albert the Great. Albert expressed interest in Aristotle, although his interpretation of the Greek philosopher was not as deep as Thomas’ would later be. In addition to Aristotle, Albert found inspiration from Islamic and Jewish theologians. Many thinkers in Judaism and the Arab world were themselves passionate enthusiasts of Aristotelianism.
Averroes, an Arab interpreter of Aristotle, was an important influence on Aquinas. The Arab Muslim thinker sought to reconcile the Greek Classical tradition with his own religion of Islam. Maimonides, a Jewish thinker, attempted his own synthesis between Judaism and Greek philosophy. Aquinas did the same thing, but for Christianity. In Aquinas’ lifetime, all three of the Abrahamic religions were trying to level a respectable intellectual response to the powerful resurgence of Classical texts.
While the Middle Ages are often seen unfavorably compared to the luminance of the Renaissance, the Dark Ages could arguably be described as a mini-renaissance. Medieval thinkers were deeply shaped by the revival of Classical Antiquity, and Aquinas was a particularly visible example of this dynamic. In the centuries after the Crusades, the impact of Classicism would have a more pronounced and explosive effect on Western culture than in Aquinas’ time. This is in part because, in the eyes of Christendom, Aquinas had successfully managed to reconcile Aristotelianism with Christian revelation and dogmas.
None can doubt that Thomas Aquinas was a first-rate thinker. However, the brilliance of his thinking was not always recognized by the Church. Like many of the West’s greatest thinkers, Aquinas was condemned by the Church as a heretic in 1277. The Catholic clergy of the day, who were committed to an Augustinian and Platonic understanding of the Christian faith, saw Aristotle as a pagan and immoral influence.
Aristotle
Aristotle’s texts were rediscovered in Western Europe in the mid-13th century. The writings of the Greek philosopher were primarily preserved by Arab culture, and translated into Greek and Latin. Thomas Aquinas’ interest in Aristotle came from his desire to forge a new vocabulary to provide a sophisticated articulation of Christian theology.
Prior to Aquinas, Christianity had largely favored the philosophy of Plato. This had been the case since the time of Augustine. From the Fall of the Western Roman Empire until the turn of the first millennium, the connection between Christendom and ancient Greece was found in the few extant works of Plato.
By looking to Aristotle, Aquinas marked a paradigm shift within Christian thinking. He moved away from the Augustinian and Platonic tradition, toward the ideas of Aristotle. There are a number of important differences between Plato and Aristotle, regarding Christian theology. First, Aristotle was an empiricist philosopher; he was more concerned with tangible reality, rather than spirituality or metaphysical idealism. Second, Aquinas found value in Aristotle’s approach to formal logic. Syllogism became a standard method of reasoning for the medieval Scholastics. Third, Aquinas was fascinated by Aristotle’s comprehensive, encyclopedic approach to philosophy. Thomas wanted to emulate the Greek philosopher, and apply it to Christian theology. The result would be Aquinas’ Summa Theologica, which attempts to treat every domain of human knowledge well beyond just theology.
Cicero
Beyond Aristotle, Thomas absorbed influences from Cicero, who became the primary basis for his doctrine of natural law.
In On the Republic, Cicero defined natural law as a normative morality which can be discerned by human reason. The Roman philosopher felt that natural law represented a set of norms that were universally applicable, because of the human capacity to reason.
Aquinas eagerly borrowed this Stoic idea of natural law, incorporating into his view of Christian theology. In addition to natural law, Thomas theorized the existence of other types of law, such as the divine revelation found in the Bible.
Christian influences
In addition to his inspiration from Classical Antiquity, Aquinas looked to the Church Fathers of Early Christianity. He was heavily influenced by Augustine. Thomas also responded to contemporary currents of medieval Christian thought. He critiqued Anselm’s ontological argument for God’s existence. He was interested by Peter Abelard’s rationalist approach to theology.
The Scholasticism of Thomas Aquinas was such a formidable tour de force, because it attempted to harmonize faith and reason. This ambitious intellectual project was so influential on all subsequent Catholic thinking, that it became ossified as the Church’s official philosophy.
Problem of universals
Aquinas was deeply impressed by the formal logic of Classical thinkers. One of the most enduring questions he grappled with was the problem of universals.
On the one hand, there was Realism. Realism was the doctrine that metaphysical forms existed independently of their particulars. This was associated with the idealist tradition of Plato, Augustine, and Anselm.
On the other hand, there was Nominalism. Nominalism was the doctrine that only particulars exist; universals do not exist at all. In the Middle Ages, the leading supporter of this view was William of Occam. Occam became a major influence on Enlightenment empiricism, such as Hobbes and Hume.
Aquinas tried to take a middle ground, called Moderate Realism.
Summa Contra Gentiles
Aquinas’ greatest works are the Summa Theologica and the Summa Contra Gentiles. Both are huge books, and encyclopedic in their scope of topics.
The Summa Contra Gentiles was written as an apologetic for Catholic Christianity. It was intended as a justification of the religion. Thomas sought to show that Christian dogma was at least consistent with the faculties of natural reason.
For Aquinas, faith and reason were compatible, but not necessarily connected. For example, he felt that God’s existence could be proven by natural arguments, but did not feel so for Christian doctrines such as the Trinity. To Thomas, the mysteries of the Christian faith came exclusively from the divine revelation of Scripture, and could not be justified on rational grounds.
Summa Theologica
The Summa Theologica was Aquinas’ masterpiece. It was the definitive summary of Catholic theology, and still maintains that status today. In it, he gave the famous Five Ways to prove God’s existence. Those theistic arguments did not rest on claims of revelation or faith, unlike some of his other theology.
Thomas’ first three arguments were called cosmological proofs. The first was the Prime Mover argument. The second was the First Cause argument. The third argument distinguished between possible and necessary beings; it has been compared to Descartes’ Meditations. The fourth proof came from the idea of perfection, which reflects Augustinian and Platonic influences.
The final argument was the telos of nature and humanity, also known as the argument from design. This argument predates Christianity itself, but Thomas was one of its most vocal exponents. This teleological argument would later be powerfully challenged by David Hume in the 18th century, and later by Darwinian thought in the 19th century.
For Aquinas, philosophy was the handmaiden of theology. Dogma and revelation ultimately took precedence, regardless of philosophy or rational argument. But the Scholastic theologian did go to great lengths to demonstrate what he saw as the compatibility of natural reasoning with Christian beliefs.
Politics
Aquinas’ political theory was deeply shaped by his ontology. For the Scholastic thinker, the world consisted of a Great Chain of Being, with God at its peak. God was the First Mover and Uncaused Cause. Below God were incorporeal, rational beings, called angels. Then there were humans. Within humanity, there were gradations.
At the top of human society was the lawful monarch. In the Thomistic worldview, political legitimacy came from natural law and divine ordinance. This would form the basis of the divine right of kings. All other segments of feudal society were arranged in this hierarchal manner. Serfs were not allowed to challenge the monarchy. Following Aristotle’s Politics, Aquinas favored a mixed constitution. He preferred monarchy, but one conditioned by natural and divine law.
Natural law
Aquinas’ most enduring contribution to political theory was his unique formation of natural law doctrine. He distinguished between four types of law.
First, there was eternal law, or God’s providence.
Second, there was natural law. Inspired by Cicero, Thomas argued that there was a fundamental set of moral norms which were universally binding on all rational actors. Those morals did not need to come from Scripture; he saw them as being natural.
Third, there was human law. This was what the Greeks called nomos. By this, Thomas simply meant the conventional rules or norms of any given society.
Finally, there was divine law, which came from the Bible. For Thomas, it was a subset of eternal law, but specifically denoted the revelations of Scripture.
Thomas’ theory of natural law was not original. He borrowed it from the Stoics. But he incorporated and interpreted it so powerfully in his works of Catholic theology. Because of Aquinas, natural law theory has been extremely influential on Western culture and politics well beyond the Middle Ages. The notion of conscientious objection in times of war comes straight from natural law theory. The civil disobedience tradition, as practiced by Thoreau and Gandhi and Martin Luther King, all owe their existence to medieval Scholasticism.
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