Being born in medieval Italy to an aristocratic family in the year 1225 AD, St Thomas studied first at the Abbey of Monte Cassino, then at the University of Naples, and finally at the University of Paris, where one of his professors—a great philosopher and theologian in his own right—St Albertus Magnus reportedly proclaimed, in retort to another student commenting that Aquinas was a “dumb ox” due to his quiet manner, that “this dumb ox will fill the world with his bellowing!” And St Albertus Magnus was certainly correct; Aquinas is now regarded as a philosophical giant rivaling Aristotle, Kant, and the like. The importance of Aquinas to the Catholic Church in particular is beautifully summarized again by the words of his professor who, upon hearing of his death, is said to have announced that “the light of the Church has been extinguished.” The work of this Saint is so singularly forceful and unique that even today it remains entirely distinct from anything else.
But what is it about St Thomas that makes him so remarkable? In his works, the following are beautifully synthesized:
- The treatment of philosophy as a collaborative and developmental study, as opposed to a combative and separatist one
- The “contra sed contra” method of thinking
- The heavy compatibility—essentially a necessary relationship—between his philosophy and religion
To the first point, that St Thomas treats of philosophy as a collaborative and developmental study, as opposed to a combative and separatist one: while philosophers currently (since the 17th century at least) have made it a point and principle to break from tradition and start from scratch in their thinking, St Thomas held as his point and principle something altogether different—if someone were to propose to Aquinas that we should simply throw out the work of our predecessors in philosophy, he would have likely responded by pointing out the absurdity of doing the same thing in any other study. Should a physicist throw out Newton and Einstein simply because their ideas are old and were not formulated and tested entirely by that individual physicist himself, leaving himself to then sift through everything which his predecessors had already tackled? Certainly not! Anyone making a serious inquiry into the truth of things ought to examine the works of those who came before him, consider where they are compatible, where they are not, and when it is found that something is lacking, attempt to fix it; only upon finding for certain that a notion is irreconcilably broken and unamendable should it be abandoned—otherwise the thinker cuts himself off entirely from a multitude of insights he couldn’t possibly have conceived of himself (even if he arrives at some, there is no way he could possibly arrive at multiple millennia’s worth). Hence to Aquinas the notion of philosophy as developmental is paramount. He considers the views of the Mohammedans, the Atomists, the Aryans, the Aristotelians, the Jewish scholars, the Platonists, the Stoics, and many more; to St Thomas, they all have something to offer, and they all have something (he finds in most cases, many things) that can be corrected. Aristotle put it thus :
The investigation of the truth is in one way hard, in another easy. An indication of this is found in the fact that no one is able to attain the truth adequately, while, on the other hand, we do not collectively fail, but everyone says something true about the nature of things, and while individually we contribute little or nothing to the truth, by the union of all a considerable amount is amassed.
And this notion is found easily expressed in the second point, that St Thomas relies on “contra sed contra” reasoning. In Latin, the phrase “contra sed contra” means, roughly translated, “On the contrary; but on the contrary.” So “contra sed contra” reasoning is reasoning by way of an internal debate; when someone reasons contra sed contra, they put forth the best argument they can formulate or find for or against a position, refute it, offer an alternative, and—if they can—refute that as well, continuing on until the inquiry has been satisfied. This is typical and characteristic of Aquinas’ writing. In his Summa Contra Gentes, St Thomas devotes entire chapters to formulating opposing arguments in a way even better than his opponents could, only to then dedicate the next chapter to refuting said arguments, and then providing an alternative position and argument, with anticipated objections which he will then too also refute. Again, in his Summa Theologicæ, St Thomas writes in a way to purposefully emulate the university debate: question, negative arguments, positive arguments, and refutations. In this way, every truth that someone has to offer can be recognized, and every falsity that someone puts forward can be refuted.
And this leads us now to the truly remarkable feature of Thomism: its inherent Catholicity. When all the arguments have been laid out and considered, after each person’s false ideas have been refuted and each true idea championed, it is found that never is the truth in contradiction to what the Catholic Church teaches. In fact, there remains only a beautiful harmony and synthesis between the Catholic faith and reason; so St Thomas proclaims :
…whatever arguments are alleged against the teachings of faith, they do not rightly proceed from the first self-evident principles instilled by nature. Wherefore they lack the force of demonstration, and are either probable or sophistical arguments, and consequently it is possible to solve them.
After synthesizing the many philosophies which he had access to into one coherent system, the Dominican priest found that he had never departed from where his journey began; he remained just as he was as a child studying in the abbey: immersed in the Catholic faith.
 Aristotle. Met II.1, 993a–993b, trans. Ross
 Aquinas. SCG I.7, trans. Fr’s OP