that sense it is said of the earth, "it standeth for ever" (Eccles. 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." (Dt. 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. (Jn. 17:3).
Reply to Objection 1: There are said to be many eternities, accordingly as many share in eternity, by the contemplation of God.
Reply to Objection 2: The fire of hell is called eternal, only because it never ends. Still, there is change in the pains of the lost, according to the words "To extreme heat they will pass from snowy waters" (Job 24:19). Hence in hell true eternity does not exist, but rather time; according to the text of the Psalm "Their time will be for ever" (Ps. 80:16).
Reply to Objection 3: Necessary means a certain mode of truth; and truth, according to the Philosopher (Metaph. vi), is in the mind. Therefore in this sense the true and necessary are eternal, because they are in the eternal mind, which is the divine intellect alone; hence it does not follow that anything beside God is eternal.
Whether eternity differs from time?
Objection 1: It seems that eternity does not differ from time. For two measures of duration cannot exist together, unless one is part of the other; for instance two days or two hours cannot be together; nevertheless, we may say that a day or an hour are together, considering hour as part of a day. But eternity and time occur together, each of which imports a certain measure of duration. Since therefore eternity is not a part of time, forasmuch as eternity exceeds time, and includes it, it seems that time is a part of eternity, and is not a different thing from eternity.
Objection 2: Further, according to the Philosopher (Phys. iv), the "now" of time remains the same in the whole of time. But the nature of eternity seems to be that it is the same indivisible thing in the whole space of time. Therefore eternity is the "now" of time. But the "now" of time is not substantially different from time. Therefore eternity is not substantially different from time.
Objection 3: Further, as the measure of the first movement is the measure of every movement, as said in Phys. iv, it thus appears that the measure of the first being is that of every being. But eternity is the measure of the first being---that is, of the divine being. Therefore eternity is the measure of every being. But the being of things corruptible is measured by time. Time therefore is either eternity or is a part of eternity.
On the contrary, Eternity is simultaneously whole. But time has a "before" and an "after." Therefore time and eternity are not the same thing.
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.
Reply to Objection 1: Such a reason would be a valid one if time and eternity were the same kind of measure; but this is seen not to be the case when we consider those things of which the respective measures are time and eternity.
Reply to Objection 2: The "now" of time is the same as regards its subject in the whole course of time, but it differs in aspect; for inasmuch as time corresponds to movement, its "now" corresponds to what is movable; and the thing movable has the same one subject in all time, but differs in aspect a being here and there; and such alteration is movement. Likewise the flow of the "now" as alternating in aspect is time. But eternity remains the same according to both subject and aspect; and hence eternity is not the same as the "now" of time.
Reply to Objection 3: As eternity is the proper measure of permanent being, so time is the proper measure of movement; and hence, according as any being recedes from permanence of being, and is subject to change, it recedes from eternity, and is subject to time. Therefore the being of things corruptible, because it is changeable, is not measured by eternity, but by time; for time measures not only things actually changed, but also things changeable; hence it not only measures movement but it also measures repose, which belongs to whatever is naturally movable, but is not actually in motion.
The difference of aeviternity and time
Objection 1: It seems that aeviternity is the same as time. For Augustine says (Gen. ad lit. viii, 20,22,23), that "God moves the spiritual through time." But aeviternity is said to be the measure of spiritual substances. Therefore time is the same as aeviternity.
Objection 2: Further, it is essential to time to have "before" and "after"; but it is essential to eternity to be simultaneously whole, as was shown above in the first article. Now aeviternity is not eternity; for it is written (Ecclus. 1:1) that eternal "Wisdom is before age." Therefore it is not simultaneously whole but has "before" and "after"; and thus it is the same as time.
Objection 3: Further, if there is no "before" and "after" in aeviternity, it follows that in aeviternal things there is no difference between being, having been, or going to be. Since then it is impossible for aeviternal things not to have been, it follows that it is impossible for them not to be in the future; which is false, since God can reduce them to nothing.
Objection 4: Further, since the duration of aeviternal things is infinite as to subsequent duration, if aeviternity is simultaneously whole, it follows that some creature is actually infinite; which is impossible. Therefore aeviternity does not differ from time.
On the contrary, Boethius says (De Consol. iii) "Who commandest time to be separate from aeviternity."
I answer that,
