"The good of the grace of one soul is greater than the good of the nature of the whole universe"
- St Thomas Aquinas Ia IIa, q.24, a. 3, ad 2

— A Commentary on the First Part of St Thomas' Theological Summa

by Reginald Garrigou-Lagrange, O. P.


Question 10: The Eternity of God

We now come to consider eternity, because, as will at once be seen, eternity follows from immutability, since it is the duration of the absolutely immobile being. There are two things which St Thomas considers in this question: (1) eternity as such is considered in the first three questions, namely: what is eternity, whether God is eternal, whether to be eternal belongs to God alone; (2) in the remaining articles eternity is compared with created durations, that is, with reference to our continuous time, to the discrete time of the angels which is measured by their successive thoughts, and to aeviternity, or the duration of the angelic substance and the separated soul, which as substances are immutable, though they had a beginning.

In these last three articles the comparison is made from on high, namely, from eternity as it has already been defined. In the first three articles, however, there is already a similar comparison made, but it starts as it were from below, and by way of investigation finally formulates the definition of eternity.



State of the question. The definition of Boethius is the subject of inquiry. It must be observed that this definition is implied in what Holy Scripture says about God's immobility, as we shall state in the second article. Among the philosophers, Plato likewise says that time is the mobile image of immobile eternity.(2) Aristotle says equivalently, "God is the everlasting and noblest living being. In God there is both life and duration that is continual and eternal." (3) In like manner, farther on, (4) he shows that God is subsistent intellection who continually understands Himself, transcending succession of time. Moreover, Aristotle defined time as "movement that is estimated according to its before and after." (6) Thus the motion of the sun is measured in time, inasmuch as one revolution is called a day, and this day consists of distinctly different hours according to a before and after. Thus we have already at least a confused notion and a nominal definition of eternity.

Plotinus (6) explains eternity in the same way, speaking not only of the immobility of eternity but also of its indivisibility, whereas time is divided into years, days, and hours. Hence Plotinus says that, if one were to say that eternity is life interminable and totally present to itself, none of it pertaining to the past or to the future, such a one is not far from its true definition.

St. Augustine says the same,(7) speaking of the indivisible and ever constant now of eternity, whereas time is fleeting. Thus gradually the transition is effected from the nominal and confused definition to the real and distinct definition. Then Boethius (died 524) gave us the same concept of eternity in the aforesaid classical definition, saying that it is "the simultaneously-whole and perfect possession of interminable life."

St. Thomas shows here that this definition is a good one, since it is in accordance with the laws governing the search for a definition, inasmuch as by these laws there is a methodical transition from a confused to a distinct notion.(8) But St. Thomas first of all sets forth the difficulties, the two principal ones being these: (1) whole is what has parts. But this does not apply to eternity, which is simple; (2) further, if a thing is said to be whole, perfect is a superfluous addition; nor does it seem that possession implies duration.

Yet the reply is that this definition is a good one, since it properly expresses eternity as the interminable duration, which is without succession, and so it is spoken of as "being simultaneously whole."

This is not, strictly speaking, demonstrated in the body of the article, for, as it is pointed out elsewhere,(9) it is not the definition of a thing but its property that is, strictly speaking, demonstrated. The definition is sought by a certain investigation, says Aristotle,(10) by a division of its genus or quasi-genus (in the present instance, the notion of duration) and then comparing the thing to be defined with things similar and dissimilar (in the present instance, by comparing the confused notion of eternity, according to its nominal definition, with time). Yet in the body of the article there is a sort of demonstration, inasmuch as eternity is deduced from God's absolute immobility. This will be made clearer in the second article.

The argument of the article by the way of investigation may be summed up as follows: We must come to the knowledge of eternity by means of time. But time is but the numbering of movement by before and after. Contrary to this, in the duration of that which is without movement, there is absolute uniformity, without any before and after. Moreover, what is absolutely immutable is interminable, without beginning and end, whereas those things that are measured by time have a beginning and an end. Thus, therefore, eternity haso two characteristics: (i) uniformity without succession, and so it is truly spoken of as "being simultaneously whole"; (2) interminableness, so that it can be truly said to be "the simultaneously-whole and perfect possession of interminable life."

It must be observed that the first characteristic is the principal one, and so also if the movement of the heavenly bodies and time were eternal, as Aristotle thought, that is without beginning and end, time would still be distinct from eternity; for in time there is always a succession of centuries and years, although there would never have been a first or last day. Hence the principal difference between eternity and time is that the former is without before and after or that it is "being simultaneously whole."

Contrary to this, our life is not simultaneously whole, for it consists of the distinct periods of infancy, youth, adult age, prime of life, and old age. Our life is also divided into periods of labor, prayer, sleep, and the like, so that there is a great variety and instability in this succession. Hence the now of time is the current now between the past and the future, so that past and future do not actually exist but exist only in the mind, whereas the now of eternity is a standing now, which is absolutely permanent and immobile, and we find this already equivalently expressed, although less distinctly, in the writings of Plato, Aristotle, and Plotinus.

Thus the definition of Boethius is a good one, since it complies with the rules to be observed in the search for a definition. "The transition is effected methodically from a confused to a distinct notion, and this by a correct division of duration, and by a comparison of one's already confused notion of eternity with that of time.

This hunt or search presupposes the true definition of time as given by Aristotle, who says that it is movement estimated by its before and after, for example, the movement of the sun is estimated by its successive revolutions and portions of one revolution. It seems that this definition (12) is a good explanation of what is obscurely implied in the popular or common notion of time and its parts, namely, century, year, day, hour. This is the realistic notion of time. On the contrary, Kant proposed an idealist notion of time, which in his opinion is an a priori subjective form of our sensibility, in which things appear to us as a succession of phenomena.

But Kant unjustifiably denied the reality of time, giving as his reason the false antinomies that would result from this. In his opinion, it is equally demonstrated that the world had and did not have a beginning in time. But, as St. Thomas points out: "By faith alone do we hold, and by no demonstration can it be proved, that the world did not always exist."(13) God, who created with absolute freedom, could have eternally created, so that there never would have been a first day; just as the imprint of a foot in the sand would be eternal, if the foot were eternal. And even if the movement of the sun and time had been eternal creations, as we remarked, there would still be a complete distinction between time and eternity, only this latter being simultaneously whole.

The proof given in the argumentative part of the article may be presented in the following syllogistic form: What is absolutely immutable mutable is simultaneously-whole and interminable; but eternity is attributed to a thing that is absolutely immutable, just as time is attributed to things that are mobile; therefore eternity must be simultaneously-whole and interminable duration.

The solution of the difficulties confirms this conclusion.

Reply to first objection. Eternity is conceived by us as being negatively interminable, because our knowledge is first of things that come to an end.

Reply to second objection. "Interminable life" is predicated of eternity rather than "interminable being," because what is truly eternal is not only being, but also life, in fact, self-subsistent life. But life extends to operation, and not to being. Hence it is clear that both God's being and His operation are measured by eternity, whereas the angel's immutable essence and operations are not measured the same way. (14)

Reply to third objection. Eternity is called whole, not because it has parts, but inasmuch as it is wanting in nothing. In this we see the imperfection of our knowledge.

Reply to fourth objection. Sacred Scripture speaks metaphorically of the "days of eternity." (15)

Reply to fifth objection. The word perfect is not a superfluous addition, for simultaneously whole excludes past and future, and perfect excludes the passing now, which is imperfect.

Reply to sixth objection. Lastly eternity is said to be perfect possession rather than duration, to designate the indeficiency of eternity; for what is possessed, is held firmly and quietly. On the contrary, a boy does not yet possess the maturity of old age, nor does the old man possess the complete vitality of youth. So also in the interior life, the beginner does not yet possess the perfection of the unitive life.

Therefore the above definition of eternity is a very fine one, especially as regards the words "being simultaneously whole." This last expression must be the object not only of speculation, but also of acquired contemplation resulting from sacred theology, and of infused contemplation which is the result of living faith that is illumined by the gifts of intellect and wisdom.

As a, complement to this investigation into the true notion of eternity, it must be observed that great geniuses have a certain experimental knowledge of a life which by remote comparison can be called "simultaneously whole." For the most sublime manifestations of art (for instance, of music) are a certain remote participation of this kind of perfection. Thus it is said of Mozart that he heard all together a whole melody that he was composing, in that he was hearing it or previously heard it in the thought that gave it birth; whereas others heard it only successively. Thus great mathematicians by one intellectual act perceive the many elements of a very complex problem. In like manner great philosophers and theologians toward the end of their life have a sort of simultaneously whole knowledge of their science, inasmuch as they see it from on high as an irradiation of its principles. So also the contemplative experiences the joy of infused contemplation, and it remains with him during the day as a sort of latent reserve force, possessing this throughout the day as it were from on high; for when the time of prayer comes to an end, there is not a complete cessation of prayer, for it continues as it were during the time of study or even of recreation. Thus the inferiority inherent in multiplicity gradually resolves itself into the superiority of unity, and this finds its realization in the unitive life of the saints. Hence St. Augustine (16) exhorts us to a loving union with God and His eternity, peacefully awaiting the events of time, which are, as it were, beneath us, beneath the summit of the soul that is united with God.

But if Mozart heard all at once the various parts of a melody which he was composing, so we can conclude that God possesses His life all at once and sees simultaneously from on high the entire sequence of centuries. Thus eternity is like the apex of a cone, the base of which represents time. All the successive points of this base correspond to the one point of the apex.

But many difliculties, especially about the problem of evil, result from the fact that we do not see from on high the succession of time, but only successively. Thus we do not know that it is for the greater good of the world and of the Church that God permits this or that very great evil actually to happen. But if this succession of time were seen from on high by one glance, then evil would appear as a certain particularization that is a condition of the higher good, as in a picture we have the harmonious blending of light and shade, especially so in the "light transcending obscurity." In the above examples, as in that of the musical composition which is quoted by H. Bergson, there is a certain experimental knowledge of a life that bears a certain analogical resemblance to eternity. Thus the investigation is completed in a less abstract and more concrete way.

Solution of certain difficulties. As Cajetan remarks, Aureolus raised several objections against this article of St. Thomas. In the first place, he says that uniformity, because it does not differ from immutability, is not the chief characteristic of eternity.

In reply we must say with Cajetan that uniformity differs from immutability as a property differs from its essence. Immutability is the denial of the possibility of change. Uniformity adds to immutability the idea of unity of form, and this can be attributed also to motion; for we speak of uniform motion, the velocity of which is always the same, and thus it differs from variation in motion. In fact, we speak of a uniformly accelerated motion, such as the fall of a stone, or of the uniformly retarded motion of a stone thrown in the air. And just as there is uniformity in motion or succession, so also there is the same in immobility or permanence. Immutability is opposed to motion, whereas, on the other hand, uniformity is not, for there can be uniformity in motion. Consequently it is false to say that there is no distinction between uniformity and immutability. Hence eternity is correctly and more briefly defined as the uniformity of an absolutely immutable thing.

But again Aureolus objects, saying that time is not the variation of motion, and therefore uniformity is not the uniformity of the immobile.

We reply to this by distinguishing the antecedent. That time is not solely the variation of motion, this I concede; that it is not variation of motion according to before and after, this I deny. Therefore the uniformity of the immobile, in which there is no before and after, suffices for the constitution of eternity. This point will be made clearer in the following article.

Index Top


1. De Consolatione, Bk. III, pros. 2.

2. Timaeus, 37, d.

3. Metaph., Bk. XII, chap. 7 (end).

4. Ibid, chap. 9.

5 Physics, Bk. IV, chap. 11, lect. 20.

6. Enneades, IIIa, Bk. VII, chap. 4.

7. De vera religione, chap. 2, no. 97.

8. Post. Anal., Bk. II.

9. Ibid.

10. Ibid.

11. Ibid.

12. See St. Thomas' commentary on Aristotle's Physics, Bk. IV, chap. 11, lect. 20.

13. Summa theol., Ia, q.46, a.2.

14. Ibid., q. 10, a.5.

15. Mich. 5: 2.

16. Com. on Ps. 91.



"The more you know and the better you understand, the more severely will you be judged, unless your life is also the more holy. Do not be proud, therefore, because of your learning or skill. Rather, fear because of the talent given you."

Thomas á Kempis

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"It is better to be burdened and in company with the strong than to be unburdened and with the weak. When you are burdened you are close to God, your strength, who abides with the afflicted. When you are relieved of the burden you are close to yourself, your own weakness; for virtue and strength of soul grow and are confirmed in the trials of patience."

St John of the Cross, OCD - Doctor of the Church

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"God has no need of men."

St Philip Neri

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