Introduction to the Philosophy of St. Thomas Aquinas

Ch 7: The Concomitants of Motion

III. Time Cont

3. The Unity of Time and Its Standard of Measure

a) So far we have spoken of time in its general meaning. We have considered it more or less in the abstract, characterizing it as a concomitant and, in the mind, a measure of motion. Omitted from discussion have been concrete instances or systems of time. Also still unanswered is the important question whether time is one or many. Motion, of which time is a concomitant, is not all one. There are many motions all around, and many kinds, and one motion may be simultaneous with another. Does it follow that there are many times, one for each motion, and that several times may coexist?

Common experience testifies that time is basically one and the same everywhere, and this is also Aristotle's answer. There is but one time, which is the measure of all motions, whatever their kind and however their occurrence, whether in sequence or simultaneous, just as the selfsame number may be used to compute a variety of things, whatever their differences.

But if time is one, should there not also be a single motion on which all time ultimately rests and which, in consequence, serves as the standard of measure for all cosmic motion? If so, what is this unique motion? Aristotelian astronomy has a ready answer, one appropriated, virtually intact, from the appearances of sense. It is the motion of the first or outermost heaven. Because of its regularity and constancy, this motion thoroughly lends itself to being the foundation of a prime and universal measure or time.

In Aristotle's theory the unity of time hinges, therefore, on the motion of the first heaven and, in consequence, on his general scheme of cosmic motion. According to this scheme the universe is a unitary system of motion, dominated and regulated by the uniform, circular motion of the first heaven. To this motion all other motions are subordinated. In such a system it is indeed possible to discern a first or ultimate motion, even as it is possible to assign a first or ultimate principle of place; and given this system one can also fix an ultimate and universal time by which all motions are measured.

b) Such is the theory. But the same question suggests itself as in the theory of place. How much of it, if anything, is now practicable or scientifically sound? Presentday practice, it is true, still clings to the idea that time is fundamentally one and that it unfolds uniformly. Also, the standard of time continues to be set by the motion of celestial bodies. However, modern scientific thought finds it far more difficult than Aristotle, indeed seems to think it impossible, to identify a concrete motion that is primary to and the measure of all others; and in the absence of this, can there still be a unique, universal time that would be the measure of all motions? To ask this question is again to bring up the whole problem of relativity in modern physics. And again the issue cannot be resolved here. This much, however, may be said. In the matter of time, as in the theory of place, the Aristotelian position presents, no doubt, certain aspects that will not stand up in the light of contemporary scientific thought. But other aspects have proved more durable. The idea that cosmic motion is a unitary system, or that a regulating principle of time is necessary - these, if not others, are far from gone.32

c) Finally, a few words on the practical problem of measuring time. Since time is a successive continuity, it is not directly measurable, but is measured by the distance traveled by local motion. In local motion, which serves to the time that elapses and the space traveled; hence, in practice, time is measured by measuring the distance of motion. If, moreover, one assumes with Aristotle and, for that matter, with the moderns that the measuring motion is uniform, it is a simple step from the calculation of distances to the calculation of the corresponding times. As for measuring the duration of qualitative motions (local motion is quantitative), this offers no special difficulty. The characteristic moments of the qualitative change in question are noted and compared with the coincident moments in the motion used as the standard of measure. Any change that permits of such coincidences being established can be measured in time.

4. Some Related Notions: Eternity, Aevum, Duration

a) Eternity. - Though Aristotle made no separate study of the notion of eternity, it nevertheless occupies a very important place in his philosophy and, as a matter of fact, in the speculations of the ancient philosophers generally. In a primary sense eternity appears to be the prerogative of higher or supernatural beings. Thus, in the present book of the Physics 33 Aristotle remarks that eternal things, things which are always, are not in time, since their existence is not affected by time and cannot be measured by it. In Book A of the Metaphysics, in which he sets forth his natural theology, eternity is attributed to the prime mover, to pure act, which is separate, eternal, and living." But in another sense Aristotle also attributes eternity to motion." There has always been motion, he believes, and always will be. Thus the world itself is eternal.

The Christian medievals could not, of course, lend themselves to the affirmation of the world being eternal; it was, or seemed to be, in open contradiction to the dogma of creation. In fact, this thesis of Aristotle's, perhaps more than any other, was responsible for the opposition to his philosophy among some medieval masters, who, understandably, arose to declaim in the name of the faith against a too slavish acceptance of Aristotelianism. It explains, for example, St. Bonaventure's sharp criticism, though, well to remember, his immediate target was the extreme Aristotelians of his own day. These, apparently, saw nothing incongruous in their version of Aristotle not mixing with Christian teaching.

Aristotle, however, as everyone knows, had also defenders, led by St. Thomas himself. Like all Christian teachers, they acknowledged the fact of creation in time, in tern pore; but they also admitted the theoretical possibility of creation from all eternity, ab aeterno. Thus Aristotle, as they saw it, was not propounding a contradiction in terms; and if he did not know Genesis, for that he could hardly be blamed. As for the meaning of eternity in its most proper sense, St. Thomas' explicit enunciation of it occurs in the Summa in connection with his study of the divine attributes.36 This is where one should expect it, for from the Christian view eternity is primarily just that - an attribute of God, and of no other. What, then, is eternity?

If time is the measure of motion, of something possessed by degree and succession, eternity is precisely the opposite, a mode of possession not by degree or succession, but of all at once or everything together. It is the way in which a being that is utterly changeless possesses its life. The classical definition of eternity stems from Boethius (480?-524?), in whose rendering it is "the perfect and totally simultaneous possession of a life that has no limits":

interminabilis vitae tota simul et perfecta possessio.

Some clarifications may be in order. The words "interminabilis vita" (life without limits) mean that eternity has neither beginning nor end. The absence of limits is, however, secondary and accidental to eternity, even though one is sometimes led to think that it is the essential. As a matter of fact, it is quite possible to conceive of a world, or of motion, that has no beginning and no end. But all this implies is duration without determined limits, which is not the same thing as eternity proper. Eternity, in its complete meaning, presupposes utter immobility and changelessness, or, in the succinctness of Boethius, the totally simultaneous possession of one's entire life. When so understood, eternity is only in God, who alone is the substantially Eternal; of Him alone is it true to say that eternity is an essential attribute, that essence and life are one.

To be sure, the word "eternity" can be used, as already indicated, in a derivative or comparative sense, as when we speak of the eternity of the world, meaning a world without limit at either end, or, in another sense, without determinable limit. This is what the cosmologist or natural philosopher means when he raises the problem of the eternity of the world. The solution, however, lies not with him but rather with the metaphysician. St. Thomas' answer has been mentioned. For him, a world of perpetual (or, in the sense just referred to, of eternal) duration is in the realm of possibility, hence not a contradiction in terms. But faith, and faith alone, he says, teaches us that the present world had a beginning, a beginning in time, since even an eternal world must have a beginning in the sense of cause.

b) Aevum. - Only God, we have said, possesses life with perfect and totally simultaneous possession; only God is truly eternal. But there are intermediate substances between God and man, substances whose resistance to change and destruction is far above anything in the world of our experience; in fact, their nature is incorruptible, though susceptible of annihilation by the First Cause, but by no other. In the cosmology of the ancients the intelligences which were thought to move the celestial spheres, as well as the spheres themselves, were such substances. In the Christian universe angels are of this kind, though angels are not thought to inhabit the spheres. Substances of this class possess their being in more perfect manner than corporeal things have theirs, since the latter are by nature corruptible. Yet even the separate substances, as they are called, are subject to change in their accidental determinations. In the spheres of the ancients there is local motion, and the utter spirits of the Christian world think and will by thoughts and volitions that are successive. Hence, their condition is one of substantial permanence with accidental impermanence. For this mode of being Christian thought has a special name, the aevum, a sort of intermediate state between eternity and time. The accidental modifications of these substances are measured, to be sure, by a manner of time, since they occur by succession; but the time, at least of the utter spirits or angels, is discontinuous rather than, like ours, continuous.37

c) Duration. - If aevum describes a condition unfamiliar to mortals, "duration" comes much closer to home. "For the duration," to take an instance, needs no explanation to anyone; popular thought and expression abound with the idea. On another level and in our own day Bergson (1859 - 1941), a philosopher of renown, popularized a philosophy principled by the concept of duration, with, however, a meaning all his own. This is our present interest, namely, the philosophical tenor of duration and, more particularly, whether Bergson's idea of it can be fitted into Aristotelian thought.

In general, duration has a more concrete, a more stable and substantial connotation than time. What it refers to primarily is the actual existence of a thing but from a special point of view, existence in its sustained reality against the flux of accidental variations. Duration is abiding reality as compared with the succession of change, whereas time, for its part, is the measure of the succession. This, at any rate, is what duration means in the Aristotelian and Thomistic tradition.

In Bergson's philosophy the meaning is far different. Duration, according to him, is indeed the basic reality, but a reality without stability and permanence. Everything is in constant change. There is no stable subject that could be the seat of accidental change yet remain basically unchanged. If nevertheless Bergson stresses the idea of duration, he means by it not so much an abiding reality as ceaseless "creative" activity that puts duration itself in constant innovation to its very root and foundation - if indeed one may speak of root and foundation in a philosophy where nothing is even relatively permanent. In fact, wherever Bergson writes "duration," Aristotle or St. Thomas could generally rewrite "change" with no appreciable loss of meaning. Bergson's duration is not duration in the traditional sense; it is the flux of Heraclitus all over again. Furthermore, the real meaning, says Bergson, of the changes we observe lies in their qualitative succession only, and not at all in their quantitative or local motion.

Bergsonian duration, accordingly, is poles apart from Thomistic duration. Bergson denies all permanence to things, whereas in Thomistic philosophy duration is founded on the comparative permanence of substances and would have no meaning without it. Nor is Bergson's duration the same as time. Time presupposes the continuum in reality; its foundation is therefore in the order of quantity and not, like the duration of Bergson, in the order of quality. On this matter, then, one will look in vain for exact agreement between the two philosophies.


Footnotes

32 For further philosophical orientation to the question of time in the relativist setting resort may be had to V. E. Smith, Philosophical Physics, chapter 11, "Time: The Measure of motion"; also, a more mathematically-centered inspection, to A. G. Van Melsen, The Philosophy of Nature, pp. 181-194. - [Tr.]

33 IV, 12, 221 b 3.

34 Metaph. A, 6.

35 Phys. VIII, 1-2.

36 Summa theol., Ia, q. 10.

37 On the meaning of aevum, and how it differs from both time and eternity, see Summa theol., Ia. q. 10, aa. 4-6. Some helpful remarks on the notion of "discrete time" may also be found in Sister M. Jocelyn, 0.P., "Discrete Time and Illumination," Laval Theologique et Philosophique, II (2, 1946), 49-57. - [Tr.]


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