See the first post in this series for an explanation and guide.
This may be proved in three ways. The first…
Chapter 5: That those things which cannot be investigated by reason are fittingly proposed to man as an object of faith
…(4) There results also another advantage from this, namely, the checking of presumption which is the mother of error. For some there are who presume so far on their wits that they think themselves capable of measuring the whole nature of things by their intellect, in that they esteem all things true which they see, and false which they see not. Accordingly, in order that man’s mind might be freed from this presumption, and seek the truth humbly, it was necessary that certain things far surpassing his intellect should be proposed to man by God.i
(5) Yet another advantage is made apparent by the words of the Philosopher (10 Ethic.). For when a certain Simonides maintained that man should neglect the knowledge of God, and apply his mind to human affairs, and declared that a man ought to relish human things, and a mortal, mortal things: the Philosopher contradicted him, saying that a man ought to devote himself to immortal and divine things as much as he can. Hence he says (11 De Animal.) that though it is but little that we perceive of higher substances, yet that little is more loved and desired than all the knowledge we have of lower substances. He says also (2 De Coelo et Mundo) that when questions about the heavenly bodies can be answered by a short and probable solution, it happens that the hearer is very much rejoiced. All this shows that however imperfect the knowledge of the highest things may be, it bestows very great perfection on the soul: and consequently, although human reason is unable to grasp fully things that are above reason, it nevertheless acquires much perfection, if at least it hold things, in any way whatever, by faith…ii
Chapter 6: That it is not a mark of levity to assent to the things that are of faith, although they are above reason
…(4) On the other hand those who introduced the errors of the sects proceeded in contrary fashion, as instanced by Mohammed, who enticed peoples with the promise of carnal pleasures, to the desire of which the concupiscence of the flesh instigates. He also delivered commandments in keeping with his promises, by giving the reins to carnal pleasure, wherein it is easy for carnal men to obey: and the lessons of truth which he inculcated were only such as can be easily known to any man of average wisdom by his natural powers: yea rather the truths which he taught were mingled by him with many fables and most false doctrines. Nor did he add any signs of supernatural agency, which alone are a fitting witness to divine inspiration, since a visible work that can be from God alone, proves the teacher of truth to be invisibly inspired: but he asserted that he was sent in the power of arms, a sign that is not lacking even to robbers and tyrants. Again, those who believed in him from the outset were not wise men practised in things divine and human, but beastlike men who dwelt in the wilds, utterly ignorant of all divine teaching; and it was by a multitude of such men and the force of arms that he compelled others to submit to his law…iii
Chapter 7: That the truth of reason is not in opposition to the truth of the Christian faith
(1) NOW though the aforesaid truth of the Christian faith surpasses the ability of human reason, nevertheless those things which are naturally instilled in human reason cannot be opposed to this truth. For it is clear that those things which are implanted in reason by nature, are most true, so much so that it is impossible to think them to be false.iv
Nor is it lawful to deem false that which is held by faith, since it is so evidently confirmed by God. Seeing then that the false alone is opposed to the true, as evidently appears if we examine their definitions, it is impossible for the aforesaid truth of faith to be contrary to those principles which reason knows naturally.v
(2) Again. The same thing which the discipleâ€™s mind receives from its teacher is contained in the knowledge of the teacher, unless he teach insincerely, which it were wicked to say of God. Now the knowledge of naturally known principles is instilled into us by God, since God Himself is the author of our nature. Therefore the divine Wisdom also contains these principles. Consequently whatever is contrary to these principles, is contrary to the divine Wisdom; wherefore it cannot be from God. Therefore those things which are received by faith from divine revelation cannot be contrary to our natural knowledge.vi
(3) Moreover. Our intellect is stayed by contrary arguments, so that it cannot advance to the knowledge of truth. Wherefore if conflicting knowledges were instilled into us by God, our intellect would thereby be hindered from knowing the truth. And this cannot be ascribed to God.vii
(4) Furthermore. Things that are natural are unchangeable so long as nature remains. Now contrary opinions cannot be together in the same subject. Therefore God does not instill into man any opinion or belief contrary to natural Knowledge…
(7) From this we may evidently conclude that 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.viii
iModern intellectuals particularly avoid learning about or discussing God. The subject embarrasses them. At best, they might eagerly accept a weak counter-argument for God’s existence, glad to be shot of the obligation to investigate further, shoot opinions off the cuff, or quote a supposed witticism by some untutored New Atheist. Shameful behavior, really, on such an important question. Why not let’s examine the best arguments, as we should in all areas? Though St Thomas is right to emphasize that there are some things above us that we must take on faith, just as the common do when confronting most technical claims of Science—not everybody can understand all things. I repeat that we won’t be taking anything on faith, except for those bits of knowledge that come in-built (i.e. a priori knowledge).
ii“[I]t happens that the hearer is very much rejoiced“. Isn’t this what the materialist rightly says about the higher truths in Science? That knowing it depths brings joy? Knowledge is good for its own sake. It us why mathematicians call their theorems beautiful. It is why once you hear St Thomas’s arguments in Chapter 13 and beyond, you will be happy.
iiiOf course, nowadays most come to Islam via other paths, but the promised carnality doesn’t hurt. Seventy-two virgins, is it? Not that all Muslims take that belief literally, of course. However, what Thomas says applies, I think, to the current rage for materialism. I can call myself any gender I want? Sign me up. What matters is what I desire and not what is? I’m right there with you. We are running from physics and metaphysics as fast as we can, straight into the arms of ourselves.
Mark Twain thought that the lack of a carnal nature in the afterlife of Christians was an argument against belief. For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven bothered him greatly. Yet Plato in his Republic taught us that with age comes the diminishing of carnal thoughts and distractions, he showed us the great freedoms which accompanies this release.
ivNotice that this does work for propositions implanted by evolution. Suppose we were born with the innate knowledge that fire is hot because the unfit among our ancestors were burnt, much in the same way many animals are born with an innate fear of man. In this case, evolution would be creating a built-in belief which was true. But then suppose we were born with the innate idea that that we believe ideas because they make us happy and allow group cohesion, i.e. our ancestors who had happy notions bred more copiously than our ancestors who demanded proof and evidence. How would you ever know if you were a member of the former group? You could be fooling yourself that was actually false you think true because it is comforting. For example, we could be born with a gene for atheism (it can’t be that believing you are of variable “gender” or “sexuality” will help your reproductive chances). There is no reason to trust evolution leads to truth. We’re stuck with metaphysics and the grueling task of proving difficult claims.
On the other hand, there are some truths implanted in us, though not be evolution, that are true and impossible to think other than true. That a thing cannot exist and not exist simultaneously is one. That nothing which is not already actual can be a cause. That if x and y are integers and if x = y, then y = x. I don’t know if anybody has collected these truths. Would make a fascinating monograph.
vBe careful to understand Thomas is claiming a conditional true. If God told you to believe X because it is true, then X cannot be false. You needed yet believe in God to believe, which you must, that statement. See paragraph (3) for clarification.
viAnd now we see the candidate source for our a priori knowledge.
viiGod cannot lie to us (another conditional statement). But we sure can lie to ourselves (true by multiple overwhelming observation).
viiiI skipped over the (conditional) arguments about the veracity of scripture, which you won’t yet believe, and are at this point distracting. Thomas is talking to the teacher in the excised paragraphs, not the student. But here he repeats that we shall test and prove all things. I emphasize that you will not be asked to swallow anything, that all will be given ample demonstration.
Note We’re just getting past the introductory material and into the good stuff! Like I said, the juiciest bits start in Chapter 13, which I think we’ll reach in two or three weeks. Stick around.
 vii. 8
 De Part. Animal. i. 5.
 xii. 1.