Front Page Titles (by Subject) QUESTION X.: THE ETERNITY OF GOD. ( In Six Articles. ) - The Summa Theologica of St. Thomas Aquinas. Part I QQ I.-XXVI. Vol. 1.
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QUESTION X.: THE ETERNITY OF GOD. ( In Six Articles. ) - St. Thomas Aquinas, The “Summa Theologica” of St. Thomas Aquinas. Part I QQ I.-XXVI. Vol. 1. 
The “Summa Theologica” of St. Thomas Aquinas. Part I QQ I.-XXVI. Literally translated by Fathers of the English Dominican Province. Second and revised edition (London: Burns Oates and Washbourne, 1920). Vol. 1.
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THE ETERNITY OF GOD.
We must now consider the eternity of God, concerning which arise six points of inquiry: (1) What is eternity? (2) Whether God is eternal? (3) Whether to be eternal belongs to God alone? (4) Whether eternity differs from time? (5) The difference of æviternity and of time. (6) Whether there is only one æviternity, as there is one time, and one eternity?
We proceed thus to the First Article:—
Objection 1. It seems that the definition of eternity given by Boethius (De Consol. v.) is not a good one: ‘Eternity is the simultaneously-whole and perfect possession of interminable life.’ For the word interminable is a negative one. But negation only belongs to what is defective, and this does not belong to eternity. Therefore in the definition of eternity the word interminable ought not to be found.
Obj. 2. Further, eternity signifies a certain kind of duration. But duration regards existence rather than life. Therefore the word life ought not to come into the definition of eternity; but rather the word existence.
Obj. 3. Further, a whole is what has parts. But this is alien to eternity, which is simple. Therefore it is improperly said to be whole.
Obj. 4. Many days cannot occur together, nor can many times exist all at once. But in eternity days and times are in the plural, for it is said, His going forth is from the beginning, from the days of eternity(Mic. v. 2); and also it is said, According to the revelation of the mystery hidden from eternity(Rom. xvi. 25). Therefore eternity is not omnisimultaneous.
Obj. 5. Further, the whole and the perfect are the same thing. Supposing, therefore, that it is whole, it is superfluously described as perfect.
Obj. 6. Further, duration does not imply possession. But eternity is a kind of duration. Therefore eternity is not possession.
I answer that, As we attain to the knowledge of simple things by way of compound things, so we must 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 and 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.
Reply Obj. 1. Simple things are usually defined by way of negation; as ‘a point is that which has no parts.’ Yet this is not to be taken as if the negation belonged to their essence, but because our intellect which first apprehends compound things, cannot attain to the knowledge of simple things except by removing the composite.
Reply Obj. 2. What is truly eternal, is not only being, but also living; and life extends to operation, which is not true of being. Now the protraction of duration seems to belong to operation rather than to being; hence time is the numbering of movement.
Reply Obj. 3. Eternity is called whole, not because it has parts, but because it is wanting in nothing.
Reply Obj. 4. As God, although incorporeal, is named in Scripture metaphorically by corporeal names, so eternity though simultaneously whole, is called by names implying time and succession.
Reply Obj. 5. Two things are to be considered in time: time itself, which is successive; and the now of time, which is imperfect. Hence the expression simultaneously-whole is used to remove the idea of time, and the word perfect is used to exclude the now of time.
Reply Obj. 6. Whatever is possessed, is held firmly and quietly; therefore to designate the immutability and permanence of eternity, we use the word possession.
We proceed thus to the Second Article:—
Objection 1. It seems that God is not eternal. For nothing made can be predicated of God. But eternity is a thing made; for Boethius says (De Trin. iv.) that, The now that flows away makes time, the now that stands still makes eternity; and Augustine says (Octog. Tri. Quæst. qu. 28) that God is the author of eternity. Therefore God is not eternal.
Obj. 2. Further, what is before eternity, and after eternity, is not measured by eternity. But, as Aristotle says (De Caus.), God is before eternity and He is after eternity: for it is written that the Lord shall reign for eternity, and beyond*(Exod. xv. 18). Therefore to be eternal does not belong to God.
Obj. 3. Further, eternity is a kind of measure. But to be measured belongs not to God. Therefore it does not belong to Him to be eternal.
Obj. 4. Further, in eternity there is no present, past, nor future, since it is simultaneously whole; as was said in the preceding article. But words denoting present, past, and future time are applied to God in Scripture. Therefore God is not eternal.
On the contrary, Athanasius says in his Creed: The Father is eternal, the Son is eternal, the Holy Ghost is eternal.
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.
Reply Obj. 1. The now that stands still, is said to make eternity according to our apprehension. As the apprehension of time is caused in us by the fact that we apprehend the flow of the now; so the apprehension of eternity is caused in us by our apprehending the now standing still. When Augustine says that God is the author of eternity, this is to be understood of participated eternity. For God communicates His eternity to some in the same way as He communicates His immutability.
Reply Obj. 2. From this appears the answer to the second objection. For God is said to be before eternity, according as it is shared by immaterial substances. Hence, also, in the same book, it is said that intelligence is equal to eternity. In the words of Exodus, The Lord shall reign for eternity, and beyond, eternity stands for age, as another rendering has it. Thus, it is said that the Lord will reign beyond eternity, inasmuch as He endures beyond every age, that is, beyond every kind of given duration. For age is nothing more than the period of each thing, as is said in the book De Cælo i. Or to reign beyond eternity can be taken to mean that if any other thing were conceived to exist for ever, as the movement of the heavens according to some philosophers, then God would still reign beyond, inasmuch as His reign is simultaneously whole.
Reply Obj. 3. Eternity is nothing else but God Himself. Hence God is not called eternal, as if He were in any way measured; but the idea of measurement is there taken according to the apprehension of our mind alone.
Reply Obj. 4. Words denoting different times are applied to God, because His eternity includes all times; not as if He Himself were altered through present, past, and future.
We proceed thus to the Third Article:—
Objection 1. It seems that it does not belong to God alone to be eternal. For it is written, that those who instruct many to justice, shall be as stars unto perpctual eternities*(Dan. xii. 3). Now if God alone were eternal, there could not be many eternities. Therefore God alone is not the only eternal.
Obj. 2. Further, it is written, Depart, ye cursed, into eternal (Douay, everlasting) fire(Matt. xxv. 41). Therefore God is not the only eternal.
Obj. 3. Further, every necessary thing is eternal. But there are many necessary things; as, for instance, all principles of demonstration, and all demonstrative propositions. Therefore God is not the only eternal.
On the contrary, Jerome says (Ep. ad Damasum, xv.) that God is the only one who has no beginning. Now whatever has a beginning, is not eternal. Therefore God is the only one eternal.
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. IX. 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, that it standeth for ever(Eccl. i. 4). Again some things are called eternal in Scripture because of the length of their duration, although they are in nature corruptible; thus (Ps. lxxv. 5) the hills are called eternal, and we read of the fruits of the eternal hills(Deut. xxxiii. 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 xvii. 3).
Reply Obj. 1. There are said to be many eternities, accordingly as many share in eternity, by the contemplation of God.
Reply Obj. 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 xxiv. 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. lxxx. 16).
Reply Obj. 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.
We proceed thus to the Fourth Article:—
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 and 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.
Obj. 2. Further, according to the Philosopher (Physic. 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.
Obj. 3. Further, as the measure of the first movement is the measure of every movement, as said in Physic. 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 the 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 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 Obj. 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 Obj. 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 as being here and there; and such alternation 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 Obj. 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.
We proceed thus to the Fifth Article:—
Obj. 1. It seems that æviternity is the same as time. For Augustine says (Gen. ad. lit. viii. 20, 22, 23), that God moves the spiritual creature through time. But æviternity is said to be the measure of spiritual substances. Therefore time is the same as æviternity.
Obj. 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 æviternity is not eternity; for it is written (Ecclus. i. 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.
Obj. 3. Further, if there is no before and after in æviternity, it follows that in æviternal things there is no difference between being, having been, or going to be. Since then it is impossible for æviternal 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.
Obj. 4. Further, since the duration of æviternal things is infinite as to subsequent duration, if æviternity is simultaneously whole, it follows that some creature is actually infinite; which is impossible. Therefore æviternity does not differ from time.
On the contrary, Boethius says (De. Consol. iii), Who commandest time to be separate from æviternity.
I answer that, Æviternity 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, æviternity, 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 æviternal 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, æviternity 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 æviternity 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 æviternity has before and after, it must follow that with the receding of the first part of æviternity, the after part of æviternity must newly appear; and thus innovation would occur in æviternity 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 æviternal thing is neither inveterable, 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 æviternity, 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; æviternity 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.
Reply Obj. 1. Spiritual creatures as regards successive affections and intelligences, are measured by time. Hence also Augustine says (ibid.), that to be moved through time, is to be moved by affections. But as regards their nature they are measured by æviternity; whereas as regards the vision of glory, they have a share of eternity.
Reply Obj. 2. Æviternity is simultaneously whole; yet it is not eternity, because before and after are compatible with it.
Reply Obj. 3. In the very being of an angel considered absolutely, there is no difference of past and future, but only as regards accidental changes. Now to say that an angel was, or is, or will be, is to be taken in a different sense according to the acceptation of our intellect, which apprehends the angelic existence by comparison with different parts of time. But when we say that an angel is, or was, we suppose something, which being supposed, its opposite is not subject to the divine power. Whereas when we say he will be, we do not as yet suppose anything. Hence, since the existence and non-existence of an angel considered absolutely is subject to the divine power, God can make the existence of an angel not future; but He cannot cause him not to be while he is, or not to have been, after he has been.
Reply Obj. 4. The duration of æviternity is infinite, forasmuch as it is not finished by time. Hence, there is no incongruity in saying that a creature is infinite, inasmuch as it is not ended by any other creature.
We proceed thus to the Sixth Article:—
Objection 1. It seems that there is not only one æviternity; for it is written in the apocryphal books of Esdras: Majesty and power of ages are with Thee, O Lord.
Obj. 2. Further, different genera have different measures. But some æviternal things belong to the corporeal genus, as the heavenly bodies; and others are spiritual substances, as the angels. Therefore there is not only one æviternity.
Obj. 3. Further, since æviternity is a term of duration, where there is one æviternity, there is also one duration. But not all æviternal things have one duration, for some begin to exist after others; as appears in the case especially of human souls. Therefore there is not only one æviternity.
Obj. 4. Further, things not dependent on each other, do not seem to have one measure of duration; for there appears to be one time for all temporal things; since the first movement, measured by time, is in some way the cause of all movement. But æviternal things do not depend on each other, for one angel is not the cause of another angel. Therefore there is not only one æviternity.
On the contrary, Æviternity is a more simple thing than time, and is nearer to eternity. But time is one only Therefore much more is æviternity one only.
I answer that, A twofold opinion exists on this subject. Some say there is only one æviternity; others that there are many æviternities. 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 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 (Cæl. 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 æviternities, as there are many æviternal things of first degree. But according to the second opinion, it would be necessary to say that there is one æviternity only; because since each thing is measured by the most simple element of its genus, it must be that the existence of all æviternal things should be measured by the existence of the first æviternal thing, which is all the more simple the nearer it is to the first. Wherefore because the second opinion is the truer, as will be shown later (Q. XLVII. A. 2); we concede at present that there is only one æviternity.
Reply Obj. 1. Æviternity is sometimes taken for age, that is, a space of a thing’s duration; and thus we say many æviternities when we mean ages.
Reply Obj. 2. Although the heavenly bodies and spiritual things differ in the genus of their nature, still they agree in having a changeless being, and are thus measured by æviternity.
Reply Obj. 3. All temporal things did not begin together; nevertheless there is one time for all of them, by reason of the first measured by time; and thus all æviternal things have one æviternity by reason of the first, though all did not begin together.
Reply Obj. 4. For things to be measured by one, it is not necessary that the one should be the cause of all, but that it be more simple than the rest.
[* ]Douay,—for ever and ever.
[* ]Douay,—for all eternity.