I am presently reading through Francis Schaeffer's How Should We Then Live?, subtitled "The Rise and Decline of Western Thought and Culture". In this book, Schaeffer examines the way in which cultural worldviews have led to the rise and decline of various civilizations. The second chapter tackles the Middle Ages and the lessons about world views to be learned from that history. In addition to the book, Schaeffer has also produced a video series by the same name.
While I find the book very interesting, he has made a statement which I think may lead to some confusion about the views of St. Thomas Aquinas. Specifically, Schaeffer says:
Aquinas's contributions to Western thought is, of course, much richer than we can discuss here, but his view of man demands our attention. Aquinas held that man had revolted against God and thus had fallen, but Aquinas had an incomplete view of the Fall. He thought that the Fall did not affect man as a whole but only in part. In his view the will was fallen or corrupted but the intellect was not affected. Thus, people could rely on their own human wisdom, and this meant that people were free to mix the teachings of the Bible with the teaching of the non-Christian philosophers.
* * * As a result of this emphasis, philosophy was gradually separated from revelation--from the Bible--and philosophers began to act in an increasingly independent, autonomous manner.
Somehow, this statement has led to the assumption that Aquinas taught that man could arrive at an independent understanding of God absent the revelation of scripture.
We have to be very careful about what Schaeffer actually said in his book, and what Aquinas actually wrote. Both are being mischaracterized here. First, Schaeffer doesn't say that Aquinas was claiming that true knowledge of God could be aquired through reason alone without revelation. Instead, he is saying that Aquinas's view of the non-fallen intellect gave license to philosophers to opine about God without having to resort to Biblical passages for their evidence. Reason alone could lead them to reach some conclusions about God. Hence, Aquinas used the thoughts of Aristotle and Cicero and others to establish truths about God even though these men weren't Christian and had no knowledge of the Bible.
But what Schaeffer doesn't say and what Aquinas didn't teach was that revelation was not necessary to reach a true, accurate and complete picture about God. In the very first Article in his work, Summa Theologicae, Aquinas examined the question of "Whether it is necessary to have another doctrine besides philosophical disciplines." His answer: yes. Specifically, as translated here, Aquinas said:
It must be said that, besides the philosophical disciplines which are investigated by human reason, another doctrine based on revelation was necessary for human well-being. Such is true, in the first place, because man is ordered by God to a certain end which exceeds the grasp of reason. As Isaiah says, "Eye has not seen, God, without you, what you have prepared for those who love you" (lsa. 64:4). The end must be fore known to man, however, since he must order his intentions and actions to that end. Thus it was necessary to human well-being that certain things exceeding human reason be made known to man through divine revelation.
Even in the case of those things which can be investigated by human reason, it was necessary for man to be instructed by divine revelation. The truth concerning God, if left to human reason alone, would have appeared only to a few, and only after a long search, and even then mixed with many errors; yet all of man's well-being, which is in God, depends on knowledge of this truth. Thus, in order that this well-being should become known to men more commonly and more securely, it was necessary that they be instructed by divine revelation.
Thus it was necessary that, besides the philosophical doctrines which can be investigated by reason, there be a sacred doctrine known through revelation.
Thus, to the extent that some may intrepret Schaeffer to claim that man Aristotle taught that man could arrive at a true, accurate and complete knowledge of God without reference to the scriptures, unless Schaeffer expanded his teachings elsewhere to make such a claim, I think that it is a misunderstanding of what Scheaffer had to say. It certainly isn't what Aquinas taught.