Around 1200 CE there was a renowned scholar named Albert the Great. Up until that time the thought of Plato had dominated the philosophical and theological world. Oddly enough, the works of Aristotle had been pretty much ignored by scholars. Indeed, they were hardly ever translated from Greek into Latin, French, and German. On the other hand, Arab thinkers such as Avicenna and Averroes, had been studying and translating the works of Aristotle for a number of years immersing themselves in Aristotle’s philosophy and applying it to their own Muslim thought.
Albert thought that a Christian philosophy based on Aristotle’s philosophy might make an excellent way for Christian thinkers to engage with, indeed perhaps even convert, Muslim thinkers to Christianity. Then along came young Thomas Aquinas who signed up to study with Albert, whom I like to call “Big Al”, and he took up the challenge to develop a Christian philosophical theology based on the thought of Aristotle. Aquinas produced many volumes of what we call today “Catholic Theology” even though the distinction between Protestants and Catholics had not yet been developed.
Aquinas’ theology laid the foundation for all subsequent Catholic thought, which was seriously challenged by the Protestant theology developed by Martin Luther and John Calvin a few centuries later. In many ways Aquinas developed Catholic thought quite in accord with the philosophy of Aristotle, but he saw to it that his development thereof coincided with traditional Christian theology as well. The “invention” of British Anglicanism under Henry the Eighth sought to unite these two strands of Christian theology, but only resulted in the Anglican Church.
Aquinas distinguished between “natural theology” and “revealed theology”, the former based on pure human reason and the latter based on faith alone. The church, according to Aquinas, defined and dispensed the latter, while pure philosophical reason was responsible for the former. One of the chief difficulties with which Catholic thought has had to wrestle is the conceptual problems which derive from this sort of bifurcation, whereas Protestant thought has largely relied upon faith and the scripture with which to work out the ramifications of its views.
One place where it is possible to see the clear-cut influence of Aristotle’s philosophy on Thomas’ thought, and thus on Catholic theology, is in relation to our understanding of God. Whereas many if not most Protestant theologians would say that Christian belief is based on faith and/or the Bible, Catholic thinkers argue that it is possible to base Christian belief on pure reason alone. The arguments they use to accomplish this are borrowed directly from Aristotle.
Aquinas offered five proofs of the existence of God based on Aristotle’s thought. The first “proof” is a causal one: God is the first Cause behind all other causes. The second is a proof from motion, all things move from potentiality to actuality, and it is God who accomplishes this. The third proof is that of efficient cause, God is the actual moving force behind all motion. Next, there is the proof from degrees of perfection. God is that which is pure perfection and thus defines all modes of perfection. Finally, there is the proof from the hierarchical order of being, which implies an “ultimate orderer” being, namely God.
Thus, according to Aquinas, we can know that God exists by pure reason alone. But we can only know who God is by the revelation of scripture. We can also know something of God’s nature, according to Aquinas, by means of analogy. That is, by noting the degree to which human beings resemble God’s nature. Thus, Catholic thinkers rely more on the role of human reason than do most Protestant thinkers, all because of the radical reflections of one Albertus Magnus.