See the first post in this series for an explanation and guide.
(1) Now of all human pursuits, that of wisdom is the most perfect, the most sublime, the most profitable, the most delightful.i It is the most perfect, since in proportion as a man devotes himself to the pursuit of wisdom, so much does he already share in true happiness: wherefore the wise man says (Ecclus. xiv. 22): Blessed is the man that shall continue in wisdom…
…(2) Now in those things which we hold about God there is truth in two ways. For certain things that are true about God wholly surpass the capability of human reason, for instance that God is three and one:ii while there are certain things to which even natural reason can attain, for instance that God is, that God is one, and others like these, which even the philosophers proved demonstratively of God, being guided by the light of natural reason.iii
(3) That certain divine truths wholly surpass the capability of human reason, is most clearly evident. For since the principle of all the knowledge which the reason acquires about a thing, is the understanding of that thing’s essence, because according to the Philosopher’s teaching the principle of a demonstration is what a thing is, it follows that our knowledge about a thing will be in proportion to our understanding of its essence. Wherefore, if the human intellect comprehends the essence of a particular thing, for instance a stone or a triangle, no truth about that thing will surpass the capability of human reason.iv
But this does not happen to us in relation to God, because the human intellect is incapable by its natural power of attaining to the comprehension of His essence: since our intellect’s knowledge, according to the mode of the present life, originates from the senses: so that things which are not objects of sense cannot be comprehended by the human intellect, except in so far as knowledge of them is gathered from sensibles.v
Now sensibles cannot lead our intellect to see in them what God is, because they are effects unequal to the power of their cause. And yet our intellect is led by sensibles to the divine knowledge so as to know about God that He is, and other such truths, which need to be ascribed to the first principle. Accordingly some divine truths are attainable by human reason, while others altogether surpass the power of human reason.vi
(4) Again. The same is easy to see from the degrees of intellects. For if one of two men perceives a thing with his intellect with greater subtlety, the one whose intellect is of a higher degree understands many things which the other is altogether unable to grasp; as instanced in a yokel who is utterly incapable of grasping the subtleties of philosophy.vii
Now the angelic intellectviii surpasses the human intellect more than the intellect of the cleverest philosopher surpasses that of the most uncultured. For an angel knows God through a more excellent effect than does man, for as much as the angel’s essence, through which he is led to know God by natural knowledge, is more excellent than sensible things, even than the soul itself, by which the human intellect mounts to the knowledge of God.
And the divine intellect surpasses the angelic intellect much more than the angelic surpasses the human. For the divine intellect by its capacity equals the divine essence, wherefore God perfectly understands of Himself what He is, and He knows all things that can be understood about Him: whereas the angel knows not what God is by his natural knowledge, because the angel’s essence, by which he is led to the knowledge of God, is an effect unequal to the power of its cause.
Consequently an angel is unable by his natural knowledge to grasp all that God understands about Himself: nor again is human reason capable of grasping all that an angel understands by his natural power. Accordingly just as a man would show himself to be a most insane fool if he declared the assertions of a philosopher to be false because he was unable to understand them,ix so, and much more, a man would be exceedingly foolish, were he to suspect of falsehood the things revealed by God through the ministry of His angels, because they cannot be the object of reason’s investigations.
(5) Furthermore. The same is made abundantly clear by the deficiency which every day we experience in our knowledge of things. For we are ignorant of many of the properties of sensible things, and in many cases we are unable to discover the nature of those properties which we perceive by our senses. Much less therefore is human reason capable of investigating all the truths about that most sublime essence.
(6) With this the saying of the Philosopher is in accord (2 Metaph.) where he says that our intellect in relation to those primary things which are most evident in nature is like the eye of a bat in relation to the sun.…x
iI’ll take it we’re all on board with this. If not, this link is for you.
iiAquinas means that we cannot deduce all things; for example that God is triune, i.e. the Trinity. For this, revelation is needed. Though once that truth has been revealed, we can use it as a basis for other arguments. You, dear reader, are not yet asked to accept anything because of revelation. Aquinas’s point holds regardless.
iiiThat God exists can be known from reason and experience, as we’ll see when arriving at Chapter 13. Yes, a long way off. But so worth the effort getting there, that I’m willing to test your patience on this extended introduction. Skipping it would bespeak of laziness.
ivThe essence of a triangle is to have three straight sides with sum of angles 180 degrees and so on, and when we are finished we see that nothing about triangles escapes us. Rather, nothing escapes the man willing to put the effort into learning the essence of triangles. There is plenty we can and do know, but not everybody, and in some cases any of us, can know everything. You would think this point uncontroversial, but because of the scientism and Enlightenment ideals which infuse our culture, some people don’t like hearing it.
v“sensibles” = sensible things. Since, as it will turn out, God is infinite, and the human mind cannot encompass infinity, we cannot fully know God’s essence.
viDon’t let the first sentence slip by. Effects are not as “strong” as causes. Think of it this way. You can flick a crumb from your shirt, but somebody only seeing the effect of the crumb’s flight would not be able to infer your complete strength. An analogy for the second part: in mathematics, we can define infinity (in its various flavors) but we cannot, not ever, have direct experience of it. But knowing its definition allows us great latitude in defining and discovering mathematical propositions. The first to show where the analogy fails gets booted from class because, it should go without saying, all analogies fail by definition.
viiContra modern education “theory”, each of us ain’t as smart as the other, even though everybody thinks it. In plainer words, sometimes the failure to grasp a concept is your fault and not the author’s.
viiiAccept arguendo the existence of angels. That they exist is given to us by revelation. You do not need to accept this to profit from the argument.
ix“[A] man would show himself to be a most insane fool if he declared the assertions of a philosopher to be false because he was unable to understand them”. Repeat these words thrice.
xAnd let’s don’t forget why Socrates was so wise: he was the only man to recognize and acknowledge his limitations.
 2 Anal. Post. iii. 9.
 D. Ia. 1, 2. In future references D. stands for the Didot edition of Aristotle’s and Plato’s works