The Eternity of God

I answer that, As we attain to the knowledge of simple things by way of compound things, so must we reach to the knowledge of eternity by means of time, which is nothing but the numbering of movement by before and after. For since succession occurs in every movement, and one part comes after another, the fact that we reckon before and after in movement, makes us apprehend time, which is nothing else but the measure of before and after in movement. Now in a thing bereft of movement, which is always the same, there is no before or after. As therefore the idea of time consists in the numbering of before and after in movement; so likewise in the apprehension of the uniformity of what is outside of movement, consists the idea of eternity.

Further, those things are said to be measured by time which have a beginning and an end in time, because in everything which is moved there is a beginning, and there is an end. But as whatever is wholly immutable can have no succession, so it has no beginning, and no end.

Thus eternity is known from two sources: first, because what is eternal is interminable—that is, has no beginning nor end (that is, no term either way); secondly, because eternity has no succession, being simultaneously whole.

I answer that, The idea of eternity follows immutability, as the idea of time follows movement, as appears from the preceding article. Hence, as God is supremely immutable, it supremely belongs to Him to be eternal. Nor is He eternal only; but He is His own eternity; whereas, no other being is its own duration, as no other is its own being. Now God is His own uniform being; and hence as He is His own essence, so He is His own eternity.

I answer that, Eternity truly and properly so called is in God alone, because eternity follows on immutability; as appears from the first article. But God alone is altogether immutable, as was shown above (Q. 9, A. 1). Accordingly, however, as some receive immutability from Him, they share in His eternity. Thus some receive immutability from God in the way of never ceasing to exist; in that sense it is said of the earth, "it standeth for ever" (Eccl. 1:4). Again, some things are called eternal in Scripture because of the length of their duration, although they are in nature corruptible; thus (Ps. 75:5) the hills are called "eternal" and we read "of the fruits of the eternal hills." (Deut. 33:15). Some again, share more fully than others in the nature of eternity, inasmuch as they possess unchangeableness either in being or further still in operation; like the angels, and the blessed, who enjoy the Word, because "as regards that vision of the Word, no changing thoughts exist in the Saints," as Augustine says (De Trin. xv). Hence those who see God are said to have eternal life; according to that text, "This is eternal life, that they may know Thee the only true God," etc. (John 17:3).

I answer that, It is manifest that time and eternity are not the same. Some have founded this difference on the fact that eternity has neither beginning nor an end; whereas time has a beginning and an end. This, however, makes a merely accidental, and not an absolute difference because, granted that time always was and always will be, according to the idea of those who think the movement of the heavens goes on for ever, there would yet remain a difference between eternity and time, as Boethius says (De Consol. v), arising from the fact that eternity is simultaneously whole; which cannot be applied to time: for eternity is the measure of a permanent being; while time is a measure of movement. Supposing, however, that the aforesaid difference be considered on the part of the things measured, and not as regards the measures, then there is some reason for it, inasmuch as that alone is measured by time which has beginning and end in time. Hence, if the movement of the heavens lasted always, time would not be of its measure as regards the whole of its duration, since the infinite is not measurable; but it would be the measure of that part of its revolution which has beginning and end in time.

Another reason for the same can be taken from these measures in themselves, if we consider the end and the beginning as potentialities; because, granted also that time always goes on, yet it is possible to note in time both the beginning and the end, by considering its parts: thus we speak of the beginning and the end of a day or of a year; which cannot be applied to eternity. Still these differences follow upon the essential and primary differences, that eternity is simultaneously whole, but that time is not so.

I answer that, Aeviternity differs from time, and from eternity, as the mean between them both. This difference is explained by some to consist in the fact that eternity has neither beginning nor end, aeviternity, a beginning but no end, and time both beginning and end. This difference, however, is but an accidental one, as was shown above, in the preceding article; because even if aeviternal things had always been, and would always be, as some think, and even if they might sometimes fail to be, which is possible to God to allow; even granted this, aeviternity would still be distinguished from eternity, and from time.

Others assign the difference between these three to consist in the fact that eternity has no "before" and "after"; but that time has both, together with innovation and veteration; and that aeviternity has "before" and "after" without innovation and veteration. This theory, however, involves a contradiction; which manifestly appears if innovation and veteration be referred to the measure itself. For since "before" and "after" of duration cannot exist together, if aeviternity has "before" and "after," it must follow that with the receding of the first part of aeviternity, the after part of aeviternity must newly appear; and thus innovation would occur in aeviternity itself, as it does in time. And if they be referred to the things measured, even then an incongruity would follow. For a thing which exists in time grows old with time, because it has a changeable existence, and from the changeableness of a thing measured, there follows "before" and "after" in the measure, as is clear from Physic. iv. Therefore the fact that an aeviternal thing is neither inveterate, nor subject to innovation, comes from its changelessness; and consequently its measure does not contain "before" and "after." We say then that since eternity is the measure of a permanent being, in so far as anything recedes from permanence of being, it recedes from eternity. Now some things recede from permanence of being, so that their being is subject to change, or consists in change; and these things are measured by time, as are all movements, and also the being of all things corruptible. But others recede less from permanence of being, forasmuch as their being neither consists in change, nor is the subject of change; nevertheless they have change annexed to them either actually or potentially. This appears in the heavenly bodies, the substantial being of which is unchangeable; and yet with unchangeable being they have changeableness of place. The same applies to the angels, who have an unchangeable being as regards their nature with changeableness as regards choice; moreover they have changeableness of intelligence, of affections and of places in their own degree. Therefore these are measured by aeviternity which is a mean between eternity and time. But the being that is measured by eternity is not changeable, nor is it annexed to change. In this way time has "before" and "after"; aeviternity in itself has no "before" and "after," which can, however, be annexed to it; while eternity has neither "before" nor "after," nor is it compatible with such at all.

I answer that, A twofold opinion exists on this subject. Some say there is only one aeviternity; others that there are many aeviternities. Which of these is true, may be considered from the cause why time is one; for we can rise from corporeal things to the knowledge of spiritual things.

Now some say that there is only one time for temporal things, forasmuch as one number exists for all things numbered; as time is a number, according to the Philosopher (Physic. iv). This, however, is not a sufficient reason; because time is not a number abstracted from the thing numbered, but existing in the thing numbered; otherwise it would not be continuous; for ten ells of cloth are continuous not by reason of the number, but by reason of the thing numbered. Now number as it exists in the thing numbered, is not the same for all; but it is different for different things. Hence, others assert that the unity of eternity as the principle of all duration is the cause of the unity of time. Thus all durations are one in that view, in the light of their principle, but are many in the light of the diversity of things receiving duration from the influx of the first principle. On the other hand others assign primary matter as the cause why time is one; as it is the first subject of movement, the measure of which is time. Neither of these reasons, however, is sufficient; forasmuch as things which are one in principle, or in subject, especially if distant, are not one absolutely, but accidentally. Therefore the true reason why time is one, is to be found in the oneness of the first movement by which, since it is most simple, all other movements are measured. Therefore time is referred to that movement, not only as a measure is to the thing measured, but also as accident is to subject; and thus receives unity from it. Whereas to other movements it is compared only as the measure is to the thing measured. Hence it is not multiplied by their multitude, because by one separate measure many things can be measured.

This being established, we must observe that a twofold opinion existed concerning spiritual substances. Some said that all proceeded from God in a certain equality, as Origen said (Peri Archon. i); or at least many of them, as some others thought. Others said that all spiritual substances proceeded from God in a certain degree and order; and Dionysius (Coel. Hier. x) seems to have thought so, when he said that among spiritual substances there are the first, the middle and the last; even in one order of angels. Now according to the first opinion, it must be said that there are many aeviternities as there are many aeviternal things of first degree. But according to the second opinion, it would be necessary to say that there is one aeviternity only; because since each thing is measured by the most simple element of its genus, it must be that the existence of all aeviternal things should be measured by the existence of the first aeviternal thing, which is all the more simple the nearer it is to the first. Wherefore because the second opinion is truer, as will be shown later (Q. 47, A. 2); we concede at present that there is only one aeviternity.