There are limits to how well we can know God.
1 However, since the type of action appropriate to any agent depends on the efficacy of its active principle, and thus a thing whose heat is stronger performs the act of heating more intensely, then it must be that the manner of knowing depends on the efficacy of the principle of the act of knowing.
2 Now, the aforementioned light is a certain principle of divine knowledge, because the created intellect is elevated by it to the seeing of the divine substance. Therefore, the mode of the divine vision must be commensurate with the power of this light. Of course, the aforementioned light, in its power, falls far short of the clarity of the divine intellect. So, it is impossible for the divine substance to be seen as perfectly by means of this kind of light, as it is seen by the divine intellect itself.
Indeed, the divine intellect sees its substance as perfectly as its perfect capacity to be seen permits. In fact, the truth of the divine substance and the clarity of the divine intellect are equal, or, better, they are but one.
So, it is impossible for a created intellect, by means of the aforesaid light, to see the divine substance as perfectly as its perfect capacity to be seen permits. Now, everything that is comprehended by a knower is known by him in as perfect a way as the knowable object permits. For instance, a person who knows that a triangle has three angles equal to two right angles, but merely as a matter of opinion on the basis of probable reasoning, since it is said to be so by wise men, does not yet comprehend it; but only the man who knows this as a definite knowable object, by means of whatever is its cause. It is impossible, then, for the created intellect to comprehend the divine substance.
Notes All teachers will appreciate that analogy! That “probable reasoning” is what I elsewhere called “local truths”, and is obviously a good use of the argument by authority. The conclusion is not necessarily true, but probably true.
3 Again, a finite power in its, operation cannot be on a par with an infinite object. But the divine substance is something infinite in relation to every created intellect, since every created intellect is limited under a definite species. So, it is impossible for any created intellect’s vision to be equal to the seeing of the divine substance; that is to say, to seeing it as perfectly as its capacity to be seen permits. Therefore, no created intellect may comprehend it.
4 Besides, every agent acts perfectly to the extent that it participates in the form which is the principle of its operation. Now, the intelligible form, by which the divine substance is seen, is the divine essence itself, and, though it becomes the intelligible form of the created intellect, the created intellect does not grasp it according to its entire capacity. So, it does not see it as perfectly as its capacity to be seen permits. Therefore, it is not comprehended by the created intellect.
Notes A point which, when grasped, should produce a deep humility. The most fundamental and important stuff we know is given to us. We at best figure out tiny intellectual puzzles.
5 Furthermore, no object of comprehension exceeds the limitations of the one who comprehends. Thus, if the created intellect were to comprehend the divine substance, the divine substance would not exceed the limits of the created intellect. But this is impossible. Therefore, it is not possible for a created intellect to comprehend the divine substance.
6 Now, this statement that the divine substance is seen by the created intellect, yet not comprehended, does not mean that part of it is seen and part not seen, because the divine substance is entirely simple. Rather, it means that it is not seen as perfectly by the created intellect as its visibility would permit. In the same way, a man who has an opinion regarding a demonstrative conclusion is said to know it but not to comprehend it, since he does not know it perfectly, that is, in a scientific way, though there is no part of it that he does not know.
Notes I like to call this “owning the fact”. Students can memorize a fact, and repeat it, but their incomprehension (for the most part) about the fact does not make it false. The fact is held largely on authority, which is weak because any little thing can disturb it. Think of the premises built up about a fact, or rather from which a fact is deduced, as a sort of wall. Authority is one brick, easily assailed. But as premises (knowledge) increase, so does the strength of the wall. Losing one premise won’t make the conclusion fall.