On the other hand, there is another sort of knowledge of God, higher than the foregoing, and we may acquire it through demonstration. A closer approach to a proper knowledge of Him is effected through this kind, for many things are set apart from Him, through demonstration, whose removal enable Him to be understood in distinction from other beings. In fact, demonstration shows that God is immutable, eternal, incorporeal, altogether simple, one, and other such things which we have shown about God in Book One[15-38].
Now, we reach a proper knowledge of a thing not only through affirmations but also through negations; for instance, it is proper to a man to be a rational animal, and so it is proper to him not to be inanimate or irrational. But there is this difference between these two modes of proper knowledge: through affirmations, when we have a proper knowledge of a thing, we know what the thing is, and bow it is separated from others; but through negations, when we have a proper knowledge of a thing, we know that it is distinct from other things, yet what it is remains unknown. Now, such is the proper knowledge that we have of God through demonstrations. Of course, this is not sufficient for the ultimate felicity of man.
 For, the things which pertain to a species extend to the end of that species, in most cases; in fact, things which are of natural origin are so always, or in most cases, though they may fail in a few instances because of some corruption. Now, felicity is the end of the human species, since all men naturally desire it. So, felicity is a definite common good, capable of accruing to all men, unless an impediment occurs by which some may be deprived of it. Now, few men attain the knowledge of God that we have just mentioned, acquired by way of demonstration, because of the obstacles to this knowledge which we touched on in the beginning of this work. Therefore, such knowledge of God is not essentially identical with human felicity.
 Then, again, to be actual is the end of what is potential, as is clear from the foregoing. So, felicity which is the ultimate end is an act to which no potency for further actuality is attached. But this sort of knowledge of God, acquired by way of demonstration, still remains in potency to something further to be learned about God, or to the same knowledge possessed in a higher way, for later men have endeavored to add something pertinent to divine knowledge to the things which they found in the heritage of their predecessors. Therefore, such knowledge is not identical with ultimate felicity.
 Moreover, felicity excludes all unhappiness, for no man can be at once unhappy and happy. Now, deception and error constitute a great part of unhappiness; in fact, that is what all men naturally avoid. But manifold error can accompany the aforesaid knowledge that is acquired about God, and this is evident in many men who learned some truths about God by way of demonstration, and who, following their own opinions in cases where demonstration fails them, have fallen into many errors. In fact, if there have been any men who have discovered the truth about divine things in such a way, by means of demonstration, that no falsity attached to their judgment, it is clear that there have been few such. This is not appropriate to felicity, which is a common end. So, man’s ultimate felicity does not lie in this knowledge of God.
 Besides, felicity consists in a perfect operation. Now, certainty is required for perfect knowledge; for this reason we are not said to know unless we learn something that cannot be otherwise, as is evident in the Posterior Analytics [I, 2: 72a17]. Now, the knowledge we have been talking about includes much uncertainty; the diversity of the sciences of divine matters among those who have tried to find out these things by way of demonstration shows this. Therefore, ultimate felicity is not found in such knowledge.
 Moreover, the will rests its desire when it has attained the ultimate end. But the ultimate cud of all human knowledge is felicity. So, that knowledge of God which, when acquired, leaves no knowledge of a knowable object to be desired is essentially this felicity. But this is not the kind of knowledge about God that the philosophers were able to get through demonstrations, because, even when we acquire this knowledge, we still desire to know other things that are not known through this knowledge. Therefore, felicity is not found in such knowledge of God.
 Furthermore, the end of every being which is in potency is to be brought into act, for it tends toward this through the motion by which it is moved to its end. Of course, every being in potency tends to become actual, in so far as that is possible. Now, there is one kind of being in potency whose entire potency can be reduced to act; hence, its end is to be completely reduced to act. Thus, a heavy body in some unusual position is in potency to its proper place. But there is another kind of thing whose entire potency cannot be reduced to act at the same time. This is the case with prime matter, and that is why, through its change, it seeks to be actuated successively under different forms which cannot be simultaneously present in it, because of their diversity. Now, our intellect is in potency to all intelligible objects, as was explained in Book Two . But two intelligible objects can exist simultaneously in the possible intellect, by way of the first act which is science, though perhaps not by way of the second act which is consideration. It is evident from this that the entire potency of the possible intellect can be reduced to act at one time. So, this is required for its ultimate end which is felicity. But the aforesaid knowledge of God which can be acquired through demonstration does not do this, since, even when we possess it, We still remain ignorant of many things. Therefore, such knowledge of God is not sufficient for ultimate felicity.
Next - CONTRA GENTILES - BOOK THREE: PROVIDENCE -Chapter 40 HUMAN FELICITY DOES NOT CONSIST IN THE KNOWLEDGE OF GOD WHICH IS THROUGH FAITH