Now some, wishing to show how this can be, said that God knows singular things by universal causes. For nothing exists in any singular thing, that does not arise from some universal cause. They give the example of an astrologer who knows all the universal movements of the heavens, and can thence foretell all eclipses that are to come. This, however, is not enough; for singular things from universal causes attain to certain forms and powers which, however they may be joined together, are not individualized except by individual matter. Hence he who knows Socrates because he is white, or because he is the son of Sophroniscus, or because of something of that kind, would not know him in so far as he is this particular man. Hence according to the aforesaid mode, God would not know
singular things in their singularity.
On the other hand, others have said that God knows singular things by the application of universal causes to particular effects. But this will not hold; forasmuch as no one can apply a thing to another unless he first knows that thing; hence the said application cannot be the reason of knowing the particular, for it presupposes the knowledge of singular things.
Therefore it must be said otherwise, that, since God is the cause of things by His knowledge, as stated above (A[8]), His knowledge extends as far as His causality extends. Hence as the active power of God extends not only to forms, which are the source of universality, but also to matter, as we shall prove further on (Q[44], A[2]), the knowledge of God must extend to singular things, which are individualized by matter. For since He knows things other than Himself by His essence, as being the likeness of things, or as their active principle, His essence must be the sufficing principle of knowing all things made by Him, not only in the universal, but also in the singular. The same would apply to the knowledge of the artificer, if it were productive of the whole thing, and not only of the form.
Reply to Objection 1: Our intellect abstracts the intelligible species from the individualizing principles; hence the intelligible species in our intellect cannot be the likeness of the individual principles; and on that account our intellect does not know the singular. But the intelligible species in the divine intellect, which is the essence of God, is immaterial not by abstraction, but of itself, being the principle of all the principles which enter into the composition of things, whether principles of the species or principles of the individual; hence by it God knows not only universal, but also singular things.
Reply to Objection 2: Although as regards the species in the divine intellect its being has no material conditions like the images received in the imagination and sense, yet its power extends to both immaterial and material things.
Reply to Objection 3: Although matter as regards its potentiality recedes from likeness to God, yet, even in so far as it has being in this wise, it retains a certain likeness to the divine being.
Whether God can know infinite things?
Objection 1: It seems that God cannot know infinite things. For the infinite, as such, is unknown; since the infinite is that which, "to those who measure it, leaves always something more to be measured," as the Philosopher says (Phys. iii). Moreover, Augustine says (De Civ. Dei xii) that "whatever is comprehended by knowledge, is bounded by the comprehension of the knower." Now infinite things have no boundary. Therefore they cannot be comprehended by the knowledge of God.
Objection 2: Further, if we say that things infinite in themselves are finite in God's knowledge, against this it may be urged that the essence of the infinite is that it is untraversable, and the finite that it is traversable, as said in Phys. iii. But the infinite is not traversable either by the finite or by the infinite, as is proved in Phys. vi. Therefore the infinite cannot be bounded by the finite, nor even by the infinite; and so the infinite cannot be finite in God's knowledge, which is infinite.
Objection 3: Further, the knowledge of God is the measure of what is known. But it is contrary to the essence of the infinite that it be measured. Therefore infinite things cannot be known by God.
On the contrary, Augustine says (De Civ. Dei xii), "Although we cannot number the infinite, nevertheless it can be comprehended by Him whose knowledge has no bounds."
I answer that, Since God knows not only things actual but also things possible to Himself or to created things, as shown above (A[9]), and as these must be infinite, it must be held that He knows infinite things. Although the knowledge of vision which has relation only to things that are, or will be, or were, is not of infinite things, as some say, for we do not say that the world is eternal, nor that generation and movement will go on for ever, so that individuals be infinitely multiplied; yet, if we consider more attentively, we must hold that God knows infinite things even by the knowledge of vision. For God knows even the thoughts and affections of hearts, which will be multiplied to infinity as rational creatures go on for ever.
The reason of this is to be found in the fact that the knowledge of every knower is measured by the mode of the form which is the principle of knowledge. For the sensible image in sense is the likeness of only one individual thing, and can give the knowledge of only one individual. But the intelligible species of our intellect is the likeness of the thing as regards its specific nature, which is participable by infinite particulars; hence our intellect by the intelligible species of man in a certain way knows infinite men; not however as distinguished from each other, but as communicating in the nature of the species; and the reason is because the intelligible species of our intellect is the likeness of man not as to the individual principles, but as to the principles of the species. On the other hand, the divine essence, whereby the divine intellect understands, is a sufficing likeness of all things that are, or can be, not only as regards the universal principles, but also as regards the principles proper to each one, as shown above. Hence it follows that the knowledge of God extends to infinite things, even as distinct from each other.
Reply to Objection 1: The idea of the infinite pertains to quantity, as the Philosopher says (Phys. i). But the idea of quantity implies the order of parts. Therefore to know the infinite according to the mode of the infinite is to know part after part; and in this way the infinite cannot be known; for whatever quantity of parts be taken, there will always remain something else outside. But God does not know the infinite or infinite things, as if He enumerated part after part; since He knows all things simultaneously, and not successively, as said above (A[7]). Hence there is nothing to prevent Him from knowing infinite things.
Reply to Objection 2: Transition imports a certain succession of parts; and hence it is that the infinite cannot be traversed by the finite, nor by the infinite. But equality suffices for comprehension, because that is said to be comprehended which has nothing outside the comprehender. Hence it is not against the idea of the infinite to be comprehended by the infinite. And so, what is infinite in itself can be called finite to the knowledge of God as comprehended; but not as if it were traversable.
Reply to Objection 3: The knowledge of God is the measure of things, not quantitatively, for the infinite is not subject to this kind of measure; but it is the measure of the essence and truth of things. For everything has truth of nature according to the degree in which it imitates the knowledge of God, as the thing made by art agrees with the art. Granted, however, an actually infinite number of things, for instance, an infinitude of men, or an infinitude in continuous quantity, as an infinitude of air, as some of the ancients held; yet it is manifest that these would have a determinate and finite being, because their being would be limited to some determinate nature. Hence they would be measurable as regards the knowledge of God.
Whether the knowledge of God is of future contingent things?
Objection 1: It seems that the knowledge of God is not of future contingent things. For from a necessary cause proceeds a necessary effect. But the knowledge of God is the cause of things known, as said above (A[8]). Since therefore that knowledge is necessary, what He knows must also be necessary. Therefore the knowledge of God is not of contingent things.
Objection 2: Further, every conditional proposition of which the antecedent is absolutely necessary must have an absolutely necessary consequent. For the antecedent is to the consequent as principles are to the conclusion: and from necessary principles only a necessary conclusion can follow, as is proved in Poster. i. But this is a true conditional proposition, "If God knew that this thing will be, it will be," for the knowledge of God is only of true things. Now the antecedent conditional of this is absolutely necessary, because it is eternal, and because it is signified as past. Therefore the consequent is also absolutely necessary. Therefore whatever God knows, is necessary; and so the knowledge of God is not of contingent things.
Objection 3: Further, everything known by God must necessarily be, because even what we ourselves know, must necessarily be; and, of course, the knowledge of God is much more certain than ours. But no future contingent things must necessarily be. Therefore no contingent future thing is known by God.
On the contrary, It is written ( Ps. 32:15 ), "He Who hath made the hearts of every one of them; Who understandeth all their works," i.e. of men. Now the works of men are contingent, being subject to free will. Therefore God knows future contingent things.
I answer that, Since as was shown above (A[9]), God knows all things; not only things actual but also things possible to Him and creature; and since some of these are future contingent to us, it follows that God knows future contingent things.
In evidence of this, we must consider that a contingent thing can be considered in two ways; first, in itself, in so far as it is now in act: and in this sense it is not considered as future, but as present; neither is it considered as contingent (as having reference) to one of two terms, but as determined to one; and on account of this it can be infallibly the object of certain knowledge, for instance to the sense of sight, as when I see that Socrates is sitting down. In another way a contingent thing can be considered as it is in its cause; and in this way it is considered as future, and as a contingent thing not yet determined to one; forasmuch as a contingent cause has relation to opposite things: and in this sense a contingent thing is not subject to any certain knowledge. Hence, whoever knows a contingent effect in its cause only, has merely a conjectural knowledge of it. Now God knows all contingent things not only as they are in their causes, but also as each one of them is actually in itself. And although contingent things become actual successively, nevertheless God knows contingent things not successively, as they are in their own being, as we do but simultaneously. The reason is because His knowledge is measured by eternity, as is also His being; and eternity being simultaneously whole comprises all time, as said above (Q[10], A[2] ). Hence all things that are in time are present to God from eternity, not only because He has the types of things present within Him, as some say; but because His glance is carried from eternity over all things as they are in their presentiality. Hence it is manifest that contingent things are infallibly known by God, inasmuch as they are subject to the divine sight in their presentiality; yet they are future contingent things in relation to their own causes.
Reply to Objection 1: Although the supreme cause is necessary, the effect may be contingent by reason of the proximate contingent cause; just as the germination of a plant is contingent by reason of the proximate contingent cause, although the movement of the sun which is the first cause, is necessary. So likewise things known by God are contingent on account of their proximate causes, while the knowledge of God, which is the first cause, is necessary.