We proceed to the seventh article thus:
1. The number of the predestined does not seem to be certain. For a number which may be increased is not certain, and it appears from Deut.1:11 that the number of the predestined may be increased. "The Lord God of your fathers make you a thousand times so many as ye are." The gloss says that the number is "definite with God, who knows them that are his." Hence the number of the predestined is not certain.
2. Again, no reason can be given why God should preordain any one number to salvation rather than any other. Now God determines nothing without a reason. Hence the number of those preordained to salvation is not certain.
3. Again, the works of God are more perfect than those of nature. Now the works of nature reveal good in the many, and defect and evil in the few. It follows that if God were to determine the number of the saved, the saved would outnumber the damned. But Matt.7:13 declares the very opposite: "Wide is the gate, and broad is the way, that leadeth to destruction, and many there be which go in thereat: Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it." The number of those who will be saved cannot then be determined by God.
On the other hand: Augustine says "the number of the predestined is certain, and cannot be increased or diminished" (De Corrept. et Grat.13).
I answer: the number of the predestined is certain. Some have said that their number is formally certain, but not materially certain. This would mean that we could say with certainty that a hundred, for example, or a thousand, would be saved, but not that any particular persons would be saved. This view, however, destroys the certainty of predestination, of which we spoke in the preceding article. We must therefore affirm that the number of the predestined is known to God with material certainty, not only with formal certainty. We must declare that the number of the predestined is certain with God not only because he is aware of it, knowing how many will be saved -- indeed he knows the number of the drops of rain and of the sands of the sea with equal certainty -- but also because he chooses and determines each one.
To make this clear, we must understand that every agent intends to make something finite, as we explained when speaking of the infinite (Q.7, Arts.2, 3).  When anyone intends a determinate measure in what he makes, he thinks out the number of its essential parts, which are necessary for the perfection of the whole. But he does not select any definite number for such elements as are required only for the sake of other elements, and not as principal parts. He accepts whatever number of them may be required for the sake of the others. Thus a builder thinks out the determinate measurement of a house, the determinate number of rooms which he wishes, and the determinate numerical measurements of its walls and roof. But he does not select any definite number of stones. He accepts whatever number of stones may be required to complete the measurements of its walls. Now we must think in this way when we think of God in relation to the whole universe which he has made. He has preordained the measure in which it ought to exist, and the appropriate number of its essential parts, whose order is in a manner perpetual. He has preordained the number of worlds, the number of the stars, of the elements, and of the species of things. But individuals which pass away are not ordained for the good of the universe as principals. They are ordained secondarily, in order to preserve the good of their species. Hence although God knows the number of all individuals, he has not preordained the number of oxen, midges, and the like. His providence produces whatever number of them may be required in order to preserve their species. Now rational creatures, to a greater extent than all other creatures, are ordained for the good of the universe as principals. For in so far as they are rational, they are incorruptible -- especially those who seek to attain blessedness, since they are more immediately in touch with the final end. The number of the predestined is therefore known to God with certainty, not only because he knows it, but because he has predetermined their number as a principal.
It is not quite the same, however, with the number of the rejected. They seem to have been preordained by God for the sake of the elect, for whom "all things work together for good" (Rom.8:28). As to what the total number of the predestined may be, some say that as many men will be saved as angels have fallen. Others say that as many will be saved as angels remain. Others again say that the number of the saved will be equal to the number of fallen angels added to the whole number of angels created. But it is better said that "the number of the elect for whom there is a place in supernal happiness is known only to God."
On the first point: this quotation from Deuteronomy refers to those whose righteousness in this life was foreknown of God. The number of these both increases and diminishes, but not the number of the predestined.
On the second point: the reason for the measure of any part is to be found in its proportion to the whole. The reason why God has made so many stars, or so many species of things, and the reason why he has predestined so many, is to be found in the proportion of its principal parts to the good of the universe.
On the third point: such good as is proportionate to the normal state of nature is found in the many, and is lacking in the few. But good which exceeds the normal state of nature is found in the few, and is lacking in the many. It is obvious, for example, that the majority of men have sufficient knowledge to regulate their lives, and that those who have not are few, and are called morons or idiots, while those who attain to a profound knowledge of intelligible things are very few. Now the eternal blessedness which consists in the vision of God exceeds the normal state of nature, especially since the normal state is bereft of grace through the corruption of original sin. It is therefore the few who will be saved. Yet the mercy of God is abundantly apparent, in that very many of those whom he chooses for salvation fall short of it according to the course and inclination of nature.
 Even the infinite power of God can make only what is made, and what is made is bound to be finite, since its essential form is rendered determinate when received by its material element.