St. Thomas Aquinas was one of the rarest and most brilliant intellects in history. He was a mental polymath, conversant in theology, philosophy, logic, rhetoric, mathematics, astronomy and pagan knowledge [referred to by the Enlightenment as the 'Classics'.] Aquinas was recognized in the 13th century as a formidable intellect in an age of burgeoning real-science, experimentation, advances in math and astronomy, and a plethora of urban and ecclesiastical building. Trade was both lengthened and deepened; inventions in industry, agriculture, masonry, finance, shipping and military arms, marks out the era as one of rapid progress. Indeed the 4 centuries from roughly 900-1300 manifested the greatest increase in prosperity for the average human in history, until our own modern era.
The Catholic genius and his works are hard to master for the average modern layman. He is not an easy read. In summary we can say that Aquinas basically Christianizes Aristotle. Importantly he provides a concept of natural science, in marrying observation to experimentation and measurement, that is totally absent from Greek-Roman metaphysics. He does so to support his view that reason cannot explain all of life and certainly not the immaterial. Reason supports faith. This is called Thomist or Thomism philosophy.
I would state that Aristotle was of course wrong on many issues [see here for eg]. He was in the main a materialist and naturalist which by itself is neutral. However, unlike the Christian Scholastics of Aquinas' era in the early 13th century, Aristotle did no real scientific work. For example he claimed the earth did not move. Basic astrology/astronomy, buttressed by known mathematics in 330 BC would have allowed him to hypothesize that the earth does indeed move – and quite rapidly. The tools were available to either support or to put into doubt his own hypothesis. Within Aristotelian theory there is no known process of experimentation, testing, hypothesis refutation, observational evidence and conclusions leading to a new or improved hypothesis. Methods of science would not arrive until the age of Aquinas.
Aquinas is usually portrayed as a follower of Aristotle. This is nonsense. He was a Catholic theologian who uses Aristotle’s ideas to further support Christianity and he is especially focused on real science and methods of discovering the laws, secrets, and order of the natural world. This is the only sensible way to look at his work. During the medieval era Greek philosophical ideas in all areas had been known and debated since the time of Boethius in the 5th century. Another lie by the Marxist multiculti cult is that 'Aristotle's naturalism', or his apparent demand that you look into nature for scientific reasons as to why natural phenomena occur [no need for Zeus, Hera etc.]; only seeped into a 'dark' Europe in the 10th century via Islamic Spain, itself a nightmare of oppression, raids, intellectual suppression and Christian-hate. This is utter bunk and a-historical rewriting to support the rather insipid claim that a totalitarian cult from Mecca was somehow 'enlightened', to use the 'secular-humanist's' [Marxist-anti human] favourite term. Aristotle did not practice real science and medieval Europe was well aware of his naturalism as meagre as it truly was long before the arrival of Muhammad's cult.
The power of Thomism is that reason leads to faith; and faith supports this journey of reason to realms beyond the material. In other words, it is a sad, sorry existence if you believe that only matter is real and that all matter is some chance occurrence, randomly producing complexity. [From Étienne Gilson's The Philosophy of St. Thomas Aquinas (pgs. 37-55)]
“This transcendent influence of Faith upon Reason is an essential fact which it is important to understand, if the true features of Thomistic philosophy are to be preserved. ..This enables us to understand the admirable unity of the philosophical and the theological work of St. Thomas. It is impossible to pretend that a mind of this temper is not fully conscious of its aim. Even in the commentaries on Aristotle, his mind always knows where it is going, and there too, it works towards the doctrine of Faith, not as an explanation, but as a completion and counterpoise of mental balance. And yet one may say that St. Thomas works in the full and clear consciousness of never appealing to arguments not strictly rational, for if Faith acts upon Reason, his Reason, supported and fertilised by his Faith, does not, for all that, cease to perform purely rational operations and to assert conclusions, based only on the evidence of first principles common to all human minds.”
Faith is no enemy of reason. Indeed reason and faith are co-joined. This is one reason why the greatest scientists in history, have been deists. There is no conflict between believing in the immaterial as well as the material.
“At this point we find the reconciliation of the extreme distrust of human Reason the contempt even which St. Thomas sometimes displays towards it, with the keen taste he always retained for dialectical discussions and arguments. For when it is a question of attaining to an object which its very essence renders inaccessible to us, our Reason shows itself powerless and defective in all respects. No one was ever more convinced of this insufficiency than St. Thomas.”
Naturalism by itself, as a science, has many limitations. It cannot for example explain 'why'. Why is a single cell so complex? Yes certainly I can discover its complexity using science. But now I ask myself why do 100 Trillion of these cells co-joined in marvellous complexity, exist at all and how could these many-to-many dependencies and interactions exist by naturalist chance ?
Naturalism has never answered the question Why?. And it never will.