The whole of Christian thought may be seen as variations on the essential positions of two men—Saint Augustine and Saint Thomas Aquinas. This contention is closely related to another—that the history of philosophy is wisely seen as variations on the work of Plato and Aristotle. It is inevitable that when religious thinkers express the content of their faith, they will use the most appropriate words, concepts, and even systems available in their culture. Consequently, Augustine was a Platonist, Thomas was an Aristotelian. Any attempt to gloss over this fundamental difference between these two leading theologians of Christendom is to pervert both.
In the thirteenth century, Thomas was very influential in establishing Aristotelian empiricism, thereby creating a momentous division between philosophy and theology. Thomas held that there were certain areas unique to each discipline, while other matters could be properly understood from either perspective. The Trinity and Incarnation, for example, could be known only through revelation; the nature of the empirical world was properly the jurisdiction of philosophy and was almost perfectly understood by Aristotle. However, God’s existence, and to a certain extent his nature, could be known either through revelation or by the processes of natural reason, operating on sense perception. Thus, natural theology was strongly defended as a legitimate discipline and a fitting handmaiden of the Catholic Church.