Summa contra Gentiles1.67 Chapter LXVII. That God knows future contingent singulars

From the foregoing it is already somewhat evident that from eternity God has had unerring knowledge of singular contingencies, and that nevertheless they cease not to be contingent.

For contingency is not incompatible with certainty of knowledge except in so far as it is future, and not as it is present. Because a contingency, while future, may not be; so that the knowledge of one who thinks it will be, may be wrong, and it will be wrong if what he thinks will be, will not be. From the moment however that it is, for the time being it cannot not-be: although it may not be in the future, but this affects the contingency, not as present but as future. Hence sense loses nothing of its certainty when it sees that a man is running, although this statement is contingent. Accordingly all knowledge that bears on a contingency as present, can be certain. Now the vision of the divine intellect from eternity sees each thing that happens in time as though it were present, as we have shown above. Therefore it follows that nothing prevents God having unerring knowledge of contingencies from eternity.

Again. The contingent differs from the necessary according as each is in its cause: for the contingent is in its cause in such a way that it may not result, or may result therefrom: whereas the necessary cannot but result from its cause. But according as each of them is in itself, they differ not as to being, on which the true is founded: because there is not in the contingent, considered as it is in itself, being and not-being, but only being, although it is possible for the contingent not to be in the future. Now the divine intellect knows things from eternity, not only as to the being which they have in their causes, but also as to the being which they have in themselves. Therefore nothing prevents it having eternal and unerring knowledge of contingencies.

Moreover. Even as the effect follows certainly from a necessary cause, so does it from a complete contingent cause unless it be hindered. Now, since God knows all things, as was proved above, He knows not only the causes of contingencies, but also that which may possibly hinder them. Therefore He knows certainly whether contingencies be or not.

Again. An effect does not happen to exceed its cause; 1 Ch. lxvi. 2 Ch. lxvi. 3 Ch. 1.

but sometimes it falls short of it. Hence, since in us knowledge is caused from things, it happens at times that we know necessary things, by way not of necessity but of probability. Now, just as with us things are the cause of knowledge, so the divine knowledge is the cause of the things known. Nothing therefore prevents things whereof God has necessary knowledge being contingent in themselves.

Further. An effect cannot be necessary if its cause be contingent, for it would follow that an effect exists after its cause has been removed. Now the ultimate effect has both a proximate and a remote cause. Hence if the proximate cause be contingent, its effect must needs be contingent, even though the remote cause be necessary: thus plants do not necessarily bear fruit—although the motion of the sun is necessary—on account of the contingent intermediate causes. But God's knowledge, although it is the cause of the things it knows, is nevertheless their remote cause. Wherefore the contingency of the things it knows does not militate with its necessity: since it happens that the intermediate causes are contingent.

Again. God's knowledge would not be true and perfect, if things happened not in the same way as God knows them to happen. Now God, since He is cognizant of all being, whereof He is the source, knows each effect not only in itself, but also in its relation to every one of its causes. But the relation of contingencies to their proximate causes, is, that they result from them contingently. Therefore God knows that certain things happen and that they happen contingently. Wherefore the certainty and truth of the divine knowledge do not take away the contingency of things.

It is therefore clear from what has been said how we are to refute the objection gainsaying God's knowledge of contingencies. For change in that which is subsequent does not argue changeableness in that which precedes: since it happens that contingent ultimate effects result from necessary first causes. Now the things known to God do not precede His knowledge, as is the case with us, but are subsequent thereto. Therefore it does not follow that, if what is known to God be changeable, His knowledge can err or in any way be changeable. It will therefore be a fallacy of consequence if, because our knowledge of changeable things is changeable, we think that this happens in all knowledge.

Again, when we say God knows or knew this future thing, we imply a kind of middle term between the divine knowledge and the thing known, namely the time at which the statement is made, in relation to which that which God is said to know is future. But it is not future in relation to the divine knowledge, which existing in the moment of eternity, is related to all things as though they were present. In relation to that knowledge, if we set aside the time at which the statement is made, there is no saying that the thing is known as non-existent, so as to allow of the question being raised as to whether it is possible for the thing not to be: but it will be said to be known by God as already seen in its existence. This being supposed, there is no room for the aforesaid question: since what is already, cannot, as regards that instant, not be. The fallacy arises then from the fact that the time at which we speak is coexistent with eternity, as also does past time (which is designated when we say God knew): wherefore the relation of past or present to future time is ascribed to eternity, which is altogether inapplicable thereto. The result is a fallacy of accident.

Further, if every single thing is known to God as seen present to Him, that which God knows will be so far necessary as it is necessary that Socrates is sitting from the fact that he is seen to be sitting. Now this is necessary, not absolutely or as some say by necessity of consequent, but conditionally, or by necessity of consequence. For this conditional statement is necessary: // he is seen to sit, he sits. Wherefore if the conditional be rendered categorically, so as to run, That which is seen to sit, necessarily sits, it is clear that if it be referred to the statement, and in a composite sense, it is true, and if referred to the thing and in a divided sense, it is false. And so in these and in all like arguments employed by those who gainsay God's knowledge of contingencies, there is a fallacy of composition and division.

That God knows future contingencies is also proved by the authority of Holy Writ. For it is said (Wis. viii. 8) about the divine Wisdom: She knoweth signs and wonders before they be done, and the events of time and ages: and (Ecclus. xxxix. 24, 25): There is nothing hid from His eyes, He seeth from eternity to eternity: and (Isa. xlviii. 5): I foretold thee of old; before they came to pass I told thee.