Chapter Xxxix
THE SUMMA CONTRA GENTILES
only potentially, because the proper is only potentially contained in the common. Now happiness is a perfect operation: and man's highest good must needs be in terms of what exists actually, and not in terms of what exists only potentially; since potentiality perfected by act has the character of a good. Therefore the aforesaid knowledge of God is not sufficient for our happiness.
CHAPTER XXXIX
THAT man's happiness DOES NOT CONSIST IN THE
KNOWLEDGE OF GOD ACQUIRED BY DEMONSTRATION
There is also another knowledge of God, higher than the one just mentioned, which is acquired by means of a demonstration, and which approaches nearer to a proper knowledge of Him; for by means of a demonstration many things are removed from Him, so that in consequence we understand Him as something apart from other things. For demonstration proves that God is immovable, eternal, incorporeal, utterly simple, one, and the like, as we have shown in the First
Book. Now we arrive at the proper knowledge of a thing not only by affirmations, but also by negations. For just as it is proper to man to be a rational animal, so is it proper to him not to be inanimate or irrational. Yet there is this difference between these two modes of proper knowledge, that when we have proper knowledge of a thing by affirmations we know what that thing is, and how it is distinguished from others; whereas when we have proper knowledge of a thing by negations, we know that it is distinct from others, but remain ignorant of what it is. Such is the proper knowledge of God that can be obtained by demonstrations. But neither does this suffice for man's ultimate happiness.
For things belonging to one species for the most part attain to the end of that species, because nature achieves its purpose always or nearly always, and fails in a few instances because of some corruption. Now happiness is the end of the human species, since all men naturally desire it. Therefore happiness is a common good that can be attained by all men, unless some obstacle occur to some whereby they be deprived of it.^ Few, however, attain to the possession of the *Cf. Aristotle, Eth., I, 9 (1099b 18).
HAPPINESS AND THE KNOWLEDGE OF GOD
aforesaid knowledge of God by way of demonstration, because of the obstacles to this knowledge mentioned at the beginning of this work.^ Therefore this knowledge is not essentially man's happiness.
Again. To be actual is the end of that which exists potentially, as was made clear above.^ Therefore happiness, which is the last end, is an act free of any potentiality to a further act. Now this knowledge of God that is acquired by way of demonstration is still in potentiality to a further knowledge of God, or to the same knowledge, but by a better way: because those who came afterwards endeavored to add something to the knowledge of God besides that which they found handed down to them by those who preceded them. Therefore such knowledge is not man's ultimate happiness.
Further. Happiness excludes all unhappiness, for no man can be at the same time happy and unhappy. Now deception and error have a large place in unhappiness, since all naturally avoid them. But the aforesaid knowledge of God is subject to the admixture of many errors, as evidenced by many who knew some truths about God through demonstration, yet, following their own opinions, when they lacked proof, fell into many errors. And if there were some who by the way of demonstration discovered the truth about divine things, without any admixture of error in their opinions, it is evident that they were very few. This fact is not in keeping with happiness, which is the common end. Therefore man's ultimate happiness is not seated in such knowledge as this.
Moreover. Happiness consists in a perfect operation. Now perfect knowledge requires certitude, and that is why we cannot be said to know unless we know what cannot be otherwise, as is stated in Post. Anal, i.^ But the aforesaid knowledge is beset with uncertainty, as is clear from the diversity among sciences about divine things elaborated by those who endeavored to discover something about God by the way of demonstration. Therefore ultimate happiness does not consist in such knowledge.
Besides. When the will has obtained its last end, its desire is at rest. Now the ultimate end of all human knowledge is happiness. Therefore happiness is essentially that knowledge of God the possession of which leaves no knowledge to be
^C.G., I, 4.
^Ch. 20, 22.
*Aristotle,/'o5i. 4na/., I, 2 (72a 17).