Thomas Aquinas wrote a massive amount of material. He wrote much by dictating to scribes, and it is rumored that he could keep several going at once. Since he wrote many volumes, and it is written in a style that is not modern, he is often unread and misunderstood.
Several authors blamed him for things he did not teach. He is often blamed for planting the seeds of humanism, supposedly teaching that we can reach God through pure human reason, unaided by any divine help. This is untrue, yet several prominent authors are guilty of this.
I have utmost respect for the mind of Francis Schaeffer, but when he wrote of Thomas, he was so far off that I am convinced he never read of word of Thomas. Edward John Carnell, Cornelius Van Til, and Greg Bahnsen also misunderstood Thomas.
Carnell said “Natural theology is that method of epistemology which one follows when he seeks to establish the existence of God from an examination of the content of sense perception. Thomas Aquinas defended natural theology in classic dimensions. ‘The only road which can lead us to a knowledge of the Creator must be cut through the things of sense.'(1) ‘Faith presupposes natural knowledge, even as grace presupposes nature and perfection the perfectible.'(2) . . . Reason can demonstrate the existence of God without the aid of revelation; it works only with the data abstracted from the world of sensation.”(Carnell, Introduction to Christian Apologetics, 126-7) Bahnsen writes of “natural theology, which consists of discursive arguments that begin with observations about the natural world (e.g., that there is motion, or that the is order in nature) and then draw inferences abou the supernatural existence or character of God.”(Van Til’s Apologetic, 184) Bahnsen’s footnote about the same sentence says “For example, Thomas Aquinas maintained that ther eare some truths about God “which the natural reason is . . . able to reach . . .In fact, such truths about God have been proved demonstrably by the philosophers, guided by the light of the natural reason.”(Aquinas, Contra Gentiles, 1.3.2)
So the case these men have built about Thomas is that he claims the unaided human mind can reach God without divine aid. This is a misunderstanding of Thomas, which it is rather simple to show it is not true. The problem comes from quote-mining Thomas, or possibly focusing too much on his famous five ways to demonstrate the existence of God.
If we instead view Thomas’ works as progressive and interconnected, which in fact they are, then we learn a better answer. The very first statement in Thomas most well-known work, Summa Theologia, says the following:
It was necessary for man’s salvation that there should be a knowledge revealed by God besides philosophical science built up by human reason. Firstly, indeed, because man is directed to God, as to an end that surpasses the grasp of his reason: “The eye hath not seen, O God, besides Thee, what things Thou hast prepared for them that wait for Thee” (Isaiah 64:4) But the end must first be known by men who are to direct their thoughts and actions to the end. Hence it was necesary for the salvation of man that certain truths which exceed human reason should be made known to him by divine revelation. Even as regards those truths about God which human reason could have discovered, it was necessary that man should be taught by a divine revelation; because the truth about God such as reason could discover, would only be known by a few, and that after a long time, and with the admixture of many errors. Whereas man’s whole salvation, which is in God, depends upon the knowledge of this truth. Therefore, in order that the salvation of men might be brought about more fitly and more surely, it was necessary that they should be taught divine truths by divine revelation. It was therefore necessary that besides philosophical science built up by reason, there should be a sacred science learned through revelation. (Summa, 1.1.1)
Now, we do not know whether these men read the first page of Thomas greatest work. But we do know that they mischaracterized Thomas and presented an incomplete picture of him. Thomas is quite clear from the very beginning that man cannot reach God through human reason. The term ‘necessary’ in the quote above is a technical term, one of a fixed logical prerequisite. Man cannot reason to God without first having divine revelation, and even the things which man can reason about he still needs God’s revelation to obtain divine truth. Thomas says that even the things we can reason about we have mixed with error. Carnell’s statement that Thomas hold to reason without the aid of revelation is flatly wrong. Bahnsen and Van Til appear to have not read Thomas completely, or possibly found what their presuppositions had already convinced them was there. They too were wrong about Thomas.
Now the likes of Bahnsen and Van Til would still likely disagree with Thomas over the glimmer of human capability Thomas provides, they do not appear to realize that even this glimmer has its original source in God, not in Man. Thomas does have a high view of causation, going on to teach that man is an agent of secondary cause, fully capable of being a cause in himself, but the first cause is always God, and the secondary cause is only moved by the primary cause. Even such a reformed source as the Westminster Confession makes a distinction of primary and secondary causes.
Thomas does give a lot of ink demonstrating things of God from human sense perception. But this is a demonstration of knowledge, not a cause of knowledge, which Bahnsen and Van Til do not seem to distinguish.
(1) E. Gilson, The Philosophy of Thomas Aquinas, p. 64
(2) Aquinas, Summa, I.Q.2, A.2