The Theory of Time in Plotinus1
Unlike many important themes that are discussed or referred to here and there throughout the Enneads, Plotinus' exposition of his view on time is rather well confined to the tractate On Eternity and Time. After the section on eternity the discussion of time begins at III, vii, 7 with a critique of the most worthy of the previous speculations. An account of Plotinus' treatment of time can hardly escape a threefold division: first, the refutation of non-Aristotelian theories; second, the refutation of Aristotle; and third, the exposition of his own theory.
I
All the non-Aristotelian theories of time agree in relating time to motion (for no one ever connected it with rest); nevertheless they may be subdivided into three groups. The first of these three types of theory baldly defines time as motion. Under this classification there are some who identify time with all motion and others who restrict it to the revolution of the universe. Since Plotinus, according to his usual custom, does not name the men, one must search the sources to see whom he had in mind. Aetius, Plac. I, 22, 7, says that most of the Stoics defined time as motion itself (αυτην την χινηοιν). This may be true of a few Stoics, but Zeno, Chrysippus, and "some" Stoics fall into another group. Brehier regards Aetius' remark as a confusion.2 Aristotle also knew this theory and combats it in Physics IV, 10, 218b10ff.; but neither is he clear as to who held it. Aristotle also refers to a theory that identified time with the motion of the whole. W. D. Ross' footnote in his translation of the Physics understands Aristotle to refer to Plato. Such a representation, however, does Plato scant justice. It is probably, therefore, that Plotinus had no one definitely in mind, but was following a conventional scheme of approaching the subject. This seems all the more likely in view of the next division to be mentioned.
The second of the three types of non-Aristotelian theory, apparently a Pythagorean suggestion, identifies time with the sphere itself. Neither Aristotle, who also mentions it, nor Plotinus considers this view worthy of discussion; and a conventional scheme better than the subject-matter accounts for its inclusion.
The third type of theory is by far the most important, and its exponents can be identified. In general the position is that time is something related to motion. This something may be the interval of motion, or the measure of motion, or it may be a concomitant of motion. In each of these three subdivisions of this last type of theory, the motion involved may again be all motion in general or a particular, regular motion. In reality this third type includes all the foremost philosophers. Archytas had defined time as the number of a given motion, or, in general, as the interval proper to the nature of the universe. Plato in the Timaeus vaguely makes time some concomitant of motion. Zeno said time was the interval of motion and a measure of swiftness and slowness. And Chrysippus defined it as the concomitant interval of the motion of the world.
Each of the three types of theory, or at least the first and third, including all the subdivisions of the third, is refuted. To the first type of theory, that which identifies time with motion itself, Aristotle and Plotinus both give short refutations. A comparison shows that a basic characteristic of time underlies them both. Plotinus' first argument is as follows: Motion, whether all motion or a particular motion, is in time, and that in which the motion is must be different from the motion itself; therefore, time is not motion. These few lines, formally logical, are too brief to escape all suspicion of being a merely verbal argument, and strengthen the supposition that Plotinus is following a conventional scheme. Comparison with Aristotle's discussion of time raises the question of the exact sense of a motion's being in time. In the Physics IV, 12, 221a4, Aristotle says that to be in time means to be measured by time. He had previously said that not only is motion measured by time but, conversely, time is measured by motion, because they define each other (220b15). From this it may be concluded that time is in motion also. But if each is in the other, how can Plotinus be sure of the validity of his argument? There is nothing in this that would prevent time and motion from being really the same and differing only in ειναι. Yet this sort of difference will not satisfy Plotinus' system. Or has Plotinus some non-Aristotelian meaning for the notion of being in time? When Aristotle, on the other hand, wishes to argue against the identification of time and motion of the basis of what motion is in, he follows a different procedure. He argues that the motion of the thing is in the thing, and is where the thing is; but time is everywhere; and therefore time is not motion (218b10). Plotinus takes no account of this argument, and his substitute for it seems to be less satisfactory.
Plotinus next indicates that there are many arguments against the theory; one, however, is so convincing that no other need be developed. Motion can stop and can be intermittent, but time cannot. Time therefore cannot be motion. To the obvious reply that the revolution of the sphere is not intermittent, Plotinus answers that the revolution returns to the same point in a given time, but does not return to that point in half the time, although both the complete motion and the half-motion are the motion of the universe.3
This argument seems to be little more than a confusion between the continuous revolving of the sphere as time itself and a single revolution as a unit of time. Yet Aristotle used a similar argument. In 218a34ff. one finds: "Some say time is the motion of the world... although even the part of a revolution is a certain time, but it is not a revolution."
How is it that both Aristotle and Plotinus believe they have disposed of the theory by an objection resting on equivocation? The remarks that follow in both authors give a slim clue to the puzzle. Aristotle adds that, in case there were several heavens, the revolution of each would be a time; and there cannot be several timers at the same time. Plotinus continues to the effect that allowing the external sphere to have the most rapid motion while the inner spheres are slower ruins the theory under discussion. How does it?
Perhaps what both Aristotle and Plotinus mean to say is this. The motion of one sphere has no more claim to be time than the motion of any other sphere. Therefore, time cannot be motion, for there cannot be several times. In other words, both Aristotle and Plotinus reject the identification of time with motion because they do not believe it does justice to the unity of time. Aristotle will then preserve that unity by making time the measure of motion and by arguing that the measure is one even when the motions differ. Plotinus will aim at the same result, but in his own way.
Consequently, with the unity of time forming a major consideration in his mind, Plotinus allows his express argument to be more verbal than valid.
In the course of this unsatisfactory logomachy, Plotinus inserts a cryptic note anticipatory of his own theory. Less formal but more substantial, its successful defense would remove all need of other refutations. While it is true that the motions envisaged in this type of theory occur in time, there may be, he hints in III, vii, 8, 4, a motion that does not occur in time; and if this is so, time and motion are still further separated. What such a motion could be, he does not say at this point in the argument. Later (III, vii, 11, 15-20) he speaks of a Nature which after rest wished to rule herself and so sought a better state; she moved, and after moving somewhat she engendered the image of eternity, time. This motion of the Soul is perhaps what Plotinus has in mind. Elsewhere he says that time has its existence in the activity of the soul - how could it be otherwise? But souls are not themselves in times; only their affections and productions are; time is posterior to souls; for what is in time is inferior to time.4
After Plotinus a motion prior to time was a theme with a long history. Simplicius' account of Damascius mentions, not some activity of the Soul, but the generation of the Soul as a motion preceding time.5 This generation is neither the immutability of the higher eternal Beings, nor the ordinary time of this lower world, but an intermediary, which the Scholastics later paralleled with their αενυm. These developments are not found in Plotinus' text, but they form a commentary upon an obscure remark.
Plotinus' next concern is the Stoic theory or theories. Zeno had defined time as the interval of motion, a measure of swiftness and slowness. And this seems to have remained the common Stoic view. Chrysippus, however much he might have been honored on other points, did not win the assent of the school by restricting Zeno's definition to the motion of the world, for this restriction seemed to conflict with other Stoic tenets. Stoicism was one in holding that the world begins and ends in a conflagration, but time does not. Hence if time if the motion of the world, either time began or the world is everlasting. And neither of these could be admitted. But since Archytas as well as Chrysippus had defined time as the interval of the universal revolution, Plotinus, while he attacks Zeno's position, places more emphasis on this latter view.
Time cannot be the interval of motion because there is no one interval. Even in motion specifically the same,6 for example motion in space, there is no single interval. A unit that measures, but is different from, all intervals would have a better claim to be called time. Even if time is defined as the interval of regular motion,7 it cannot be the interval of all regular motions, for there are many such. Consequently this definition implies the impossible conclusion that there are many times.
If the notion of interval is to be used at all, it must be restricted to one, and the interval of the world's motion has the only prima facie claim to consideration. The precise significance of the word interval, however, is unclear. If it is an interval in or of the motion itself, then it is of the nature of motion only and is not time. If, on the other hand, interval refers to a quantity, it is a measure of space and is not time.8 Or does the revolution have an interval because it never ceases but always repeats itself? But this is multiplicity of motion; it is not time. In this revolving again and again, the multiplicity is merely a number like two or three, and the interval is an interval of space. Thus quantity of motion, either as a number or as an interval in space, is found, but time itself if not found. The quantity merely occurs in time, for otherwise time will not be everywhere; it will exist only in the substratum motion, and this brings us back to the discarded definition that time is motion.
An unwary defender of the theory might seek refuge in saying that it is not exactly the interval of the motion itself that is time, but the interval along which the motion progresses, an interval which also progresses with the motion, Undoubtedly this is the truth; such an interval is time; but the statement is purely verbal and is devoid of information. The original question was, What is time? And the answer has now become, Time is motion's interval in time. An interval in time would be understandable if time were first discovered.
There remains the further difficulty that, if time is the interval of motion, it is not clear what an interval of rest would be. And a frequent defect in previous theories is their failure to relate time to rest as well as to motion. The Stoic theory therefore proves to be untenable.
II
In chapter nine Plotinus turns his attention, without mentioning a name, to Aristotle's theory that time is the number, or, better,9 the measure of motion. Before launching into the main criticism, he attempts to dispose of a relatively minor point. As he did with the definition of time as the interval of motion, Plotinus again raises the question whether time can be the measure of all motion or of regular motion only. He asks, expecting a negative answer, how irregular motion could be measured. Since Aristotle explicitly included all motion in his theory, this point, though subordinate, ought not to be omitted. On Aristotelian principles the irregular motions are alteration, growth, generation, and some motions in place.10 At first sight it would seem that irregular motions in space can be measured as easily as irregular solids. Irregular motions in space are such because the body changes its direction or velocity, so that what is colloquially one motion ins strictly a composite of two motions. But each of these two is regular,11 and the gross irregular motion could be measured by combining the measurements of the parts. The other types of irregular motions, such as alteration and growth, proceeding as they do by discontinuities, may be impossible of measurement, so that on the whole, with but the one possible exception, Plotinus' rhetorical question may be justified.
But the one exception still causes difficulty. Aristotle had said that to be in time means to be measured by time. Now, if an alteration is strictly a series of discontinuous states, it may not be in time or be measured by time; but one must suppose that Plotinus would have admitted that irregular motions through space occur in time, and, if this is so, they must be measurable. To defend the denial that irregular motions can be measured, it would be necessary to give a new meaning to the phrase "to be in time." A little later, in the first half of chapter twelve and in 13, 1-3, Plotinus does in fact impose a different meaning on the phrase. To be in time comes to mean to be produced by an activity that is time or that produces time. From this it follows that the revolution of the Sun is in time; nevertheless the revolution is not measured by time, or is measured only accidentally, while time is directly measured by the revolution. And further, the time is in nothing else; but if "to be in" means "to be measured by" it would have to be in the motion that measures it. Unfortunately, nothing in this changed view of the phrase would prevent irregular motions from being measured in the same sense in which regular motions are measured. Therefore the difficulty of justifying Plotinus' question remains, and the only defensible conclusion to this introductory remark would be that an irregular motion, which for that reason must be composite, cannot be the unit of measurement. Such may have been in Plotinus' mind, for, while in a later passage he clearly distinguishes between the questions, What is time? and, What is the unit of time?, in this criticism of Aristotle the arguments evince some shifting and confusion between them.
With irregular motions presumably disposed of, the main purpose of chapter nine is to refute the Aristotelian definition that time is the number of measure of motion. Brehier's footnote at the end of the chapter in the Bude edition says, "Tout le chapitre est une critique de la theorie d'Aristote, exposee dans la Physique IV, 11-14, que Plotin suit dans tous ses details..." This note puts the matter too strongly. Plotinus does not follow Aristotle's exposition in all its details; he chooses rather to attack the one main point.
The object the of Plotinus' criticism is the definition that Aristotle placed at the end of Physics IV, 11: "Time is the number of motion with respect to before and after, and is continuous because it is an attribute of something continuous." In arriving at this definition, Aristotle had said that the number which time is, is a number in the sense of what is counted, not the number with which we count.12 And to illustrate he says that the number of a hundred horses and a hundred men is the same, but the things numbered are different.
It is not surprising that Plotinus argues against identifying time with the number by which we count. In this he is merely repeating Aristotle. But what is surprising is that the chapter as a whole does not get much beyond this denial that time is a digit, and the uncomfortable question arises, Did Plotinus completely misunderstand Aristotle? At any rate it can hardly be said that this chapter meets the Aristotelian position squarely.
To begin his refutation of the view that time is the number or measure of motion, Plotinus draws a parallel between ten horses, ten cows, ten quarts of wine or wheat, and, on the other hand, ten measures of motion. This analogy shows, as Aristotle admitted, that the number ten is no more time than it is a horse. To understand number in this sense does not enlighten us on the nature of time. If, however, time is not the ten, it may be the quart, that is, it may be a measure which has a nature of its own apart from the wheat or motions measured. Let there be then an analogy between ten quarts of win and ten measures (hours) of motion. The definition therefore identifies time with this measure. It is a quantity.
The analogy, however, suggests to one an obvious objection, for the measure of time (an hour) is not time itself but a unit of time, just as the quart, the measure of volume, is not volume itself, but a unit. The selection of a unit cannot define the nature of the thing in question. Since a quart is a limited volume, as an hour is a limited time, volume and time must first be defined before quart and hour mean anything. This is a legitimate objection, and, to be sure, Plotinus eventually raises it. He repeats it with emphasis later at the end of chapter twelve. But here in the first part of chapter nine it must be discovered between the lines, while the emphasis remains on the false concept of time as a digit.
In examining the suggestion that time is a quantity, Plotinus (line 19) changes his analogy. The quantity, instead of remaining a quart, becomes a line along with the motion.13 In this case, he argues, there is no more reason why the line should measure the motion than why the motion should measure the line. This may well be true, but, unless Plotinus shows that such a reciprocal relation cannot exist between time and motion, the point serves no purpose. Aristotle admitted that we measure motion by time and time by motion, because they define each other (220b15).
Plotinus next objects that such a line more plausibly measures the particular motion it accompanies than motion in general. In this he is deceived by his illustration. A concrete lines, a given path, may accompany but one motion; but time accompanies all. This defect in the illustration should not have been pressed to serve as a general argument. And further, it fails to meet Aristotle because Aristotle gave a reason why the same time can measure two motions (223b1ff.). It is this argument that Plotinus should have answered.
Plotinus next attempts to amplify the position that time is a quantity. Time in this theory is not a measure apart from motion but a measure along with the measured motion (line 24). The motion will be that which is measured; the quantity will be that which measures. Neither one seems to Plotinus to be time, and he makes a suggestion anticipatory of his own theory, that that which uses the measuring magnitude is time.
Finally, to dispose of the view that time is a quantity, he offers the following consideration. If time is motion measured by magnitude, and if motion cannot be measured by itself, and if therefore there must be a measure other than motion - a continuous, not a discrete, measure - then it follows that this measure or magnitude must itself be capable of being measured, if the quantity of motion is to be measured. Time therefore will be, not the magnitude running along with the motion, but the number of that magnitude. This results, however, in a digit like ten, and can refer at best to a potion of time like an hour. But time is not a portion of time.
It begins to appear that this chapter against Aristotle contains two types of argument. There are those that are sound but do not meet Aristotle's position squarely, and there are those that meet Aristotle squarely but are not sound. The rejection of the digit and the distinction between time and a unit of time may be legitimate, but neither the one nor the other undermines Aristotle's position. Aristotle explicitly rejects the former, and, as to the latter, he implies the same distinction in several sections (e.g., 220a32-b22), though perhaps not so clearly as Plotinus desired. On the other hand, the part of Plotinus' argument that seems to meet Aristotle's position is the part that is not so obviously legitimate. Let us assume a continuous measure accompanying the motion like a line: The fact that this line can itself be measured or numbered does not show that it cannot be time, for time as well as motion can be measured. This measurement no doubt would be expressed as ten hours of time. The digit ten is not time, nor is the unit hour; but contrary to Plotinus' criticism these facts do not show that the magnitude accompanying motion is not time. At best they show merely that the limited magnitude accompanying the limited motion can be only a portion of time and not time in general.
In addition to this, when Plotinus argues that the magnitude running along with the motion cannot be time, for the reason just discussed, but the number which measures the magnitude may be, he entangles himself in his own reasoning. The accompanying magnitude could not be time because it could be measured; now why cannot that which measures it be capable of being measured also? And so on to infinity, so that nothing in this series could be time.
The latter part of this chapter, from line fifty-four on, is as confused as the preceding. He begins by restating the definition: Time is that which placed alongside of motion measures it according to before and after.
An obvious criticism of this definition would be that before and after are temporal terms and cannot be given meaning until time itself has been defined. Furthermore, this criticism would meet Aristotle squarely. Aristotle had said:
The distinction of before and after holds first of all for place. It holds here because of position. Since before and after hold in magnitude, of necessity they are also found in motion. For the distinction in the latter case is analogous to that in the former. But indeed before and after also hold in time, because each corresponds to the other.14True, here Aristotle tries to avoid using temporal terms in his definition of time by referring before and after to space. But no one could have objected to Plotinus, had he questioned whether Aristotle surreptitiously passed from a spatial concept of before and after to a temporal concept. Instead of following this line of attack, however, Plotinus merely objects that "that which" is an unsatisfactory description. To say time is that which measures motion leaves it still unclear what it is that measures.
He virtually repeats his previous consideration by saying that a thing that measures motion must measure according to time and therefore it cannot be time itself. But why must this thing measure according to time in such a sense that it cannot itself be time? One must admit either that time in a sense measures according to time (and this seems possible), or that the thing which measures can itself be measured by something else and so on back to an impossible infinity.
This chapter as a whole seems to be mainly an obsession against the digit theory of time. Its defensible points are only incidentally. In addition to the ones mentioned above, there are two more legitimate considerations at the end of the chapter. The first is the argument that time exists before any (human) soul numbers or measures motion. On this point Plotinus noticeably improves on Aristotle. The second point is the brief assertion that, since time is infinite, it cannot be a number.
The analysis of this chapter has put Plotinus in a poor light. Can it be that he was confused, or stupid, or just dozing? The explanation is, not that he was confused, but at worst that he was careless and unsystematic. Chapter nine, the ostensible refutation of Aristotle, seems to fail; but chapter twelve, ostensibly an exposition of his own position, shows clearly the reasons for rejecting the Aristotelian position. But more fundamental than the explicit criticisms of Aristotle in chapter twelve is another explanation of the carelessness of chapter nine. Plotinus believed he had a better theory, a theory that could stand on its own merits without the support of arguments demolishing Aristotle. Of course, it was customary to point out mistakes of predecessors, but so superior was his positive view that he could afford a perfunctory criticism of others.
The final attempt to dispose of previous theories is the short and equally unsatisfactory argument which forms the first part of chapter ten. The view there considered defines time as an accompaniment of motion. Whom Plotinus had in mind is not clear; the definition is similar to, but broader than, that of Chrysippus, and might possibly include the view of Strato. The objection raised against it seems to be the impossibility of defining "accompany" or "to follow" before time is defined.15
Plotinus then insists on asking whether the proposed accompaniment follows after, simultaneously, or before. In any case, it is a temporal following.'16 And therefore the definition is circular, reducing, to this: Time is an accompaniment of motion in time. This is the climax and conclusion of Plotinus' perfunctory refutations. He was perfectly well acquainted with the logical sense of "follow," and in fact he uses it below on the same page (ii, 6). But by this time he had begun his positive exposition.
III
When previously before this generated the previous and needed an afterwards with it, time was resting in being and did not exist, but was itself resting quietly in that being. But an officious Nature, desiring to rule herself and to be independent and choosing to seek a fuller existence than her present state, started to move, and it [time] started too; and in the direction of everlasting succession, the posterior, the not-same but different and different again, moving a certain distance of the journey we18 produced time, having made it an image of eternity. For since in the soul there was a restless power that always wished to change what it saw there into something else, it did not care to have the whole solid completeness [of the ideal world] present with it; but just as from a seed at rest the logos unfolding itself makes an escape into multiplicity, as one would say, exhibiting the multiplicity by partition, and advances a distance to greater weakness by consuming the unity that is not in itself for the sake of its own unity; so also this power in making the visible cosmos in imitation of that one - the motion here is not that which is there, but it is similar to that which is there and wishes to be its image - first made itself temporal, having made this19 instead of eternity. Then it handed over this world to be a slave of the time so produced, having made it to be entirely in time and having encompassed all its evolutions in time, for the world moves in the Soul - there is no other place in the world for it than the Soul - and its motion is in the time inherent in the Soul. Displaying her activities one after another in an always changing succession, the Soul begets succession with her activity, and with another act of reasoning after a former one she brings forth what previously did not exist, because neither the act of reason that was produced nor the present life of the Soul is similar to her previous state. Along with the different phase of life, and by that very fact, there was a difference of time. A difference of life therefore took time, and the everlasting forward motion of life takes everlasting time, and the life that is past is past time. If therefore anyone should say that time is the life of the Soul in the motion by which it changes from one phase of life to another, he would have the right idea.In addition to this main account, it should be added that the changes in the life of the Soul are uniform, similar, silent, and continuous (12, 1-3).
Time then is defined in terms of the life of the Soul, a type of change no doubt, but a type superior to the motion of physical objects. One does not get to the bottom of things if one's attention is arrested at the motion of inanimate bodies, for their motions are imitations of the Soul's motion and they are caused by it. One must go deeper than physical motion because motion requires a spontaneity not found in the inanimate realm. The motion of the universe therefore must be explained in terms of the motion, i.e. the life of the Soul. Because the Soul produces both time and the world, this view explains why physical motion is in time, while the Soul's life is not in time (13, 30-47).
The test of this general view will now be how well it can solve the problems that arise. But before these are examined, a little clarification of the general statement may be in order with respect first to the definition itself and second to the allegation that time is an image of eternity.
It was noted that Plotinus in chapter nine failed to criticize Aristotle for passing surreptitiously from a spatial to a temporal concept of priority. The reason for this failure may be that Plotinus recognized himself to be open to a similar criticism. In II, 36-38, he uses μετα twice, εψεξης twice, and πϱοτεϱον. If the second of these is taken in its usual spatial significance, Aristotle's fault reappears. If taken in its less frequent temporal meaning, then it as well as the other two words, though temporal, has no significance until after time has been defined. They should not be used in the definition itself. And if the third word is not temporal, it must refer to a logical priority that does not clarify the concept of time. In fact, Plotinus, Aristotle, and everyone else seems to be impaled on the horns of a painful dilemma. Either the terms used in defining time are temporal, in which case they do not furnish but presuppose the definition; or the terms are not temporal, in which case there is a surreptitious passing from space to time.
So far is it from being possible that anyone should ever deduce and explain the concept of time by the help of reason, that the very principle of contradiction presupposes it, involving it as a condition. For A and not-A are not incompatible unless they are judged of the same thing together (i.e., in the same time); but when they are judged of a thing successively (i.e., at different times), they may both belong to it. Hence the possibility of changes is thinkable only in time; time is not thinkable through changes, but vice versa.But does Kant escape his own objections? Or does he escape them only by refusing to define time? His descriptions of time, at any rate, use words that presuppose the thing described. If then these considerations apply to all philosophers, Plotinus is not peculiarly unsuccessful and was perhaps wiser than Kant in not using this type of objection against his predecessors.
When Plotinus attempts to compare time and eternity, instead of signaling similarities, all his remarks are points of dissimilarity Immediately following the quotation above there is this:
For if eternity is life at rest, the same, unchanging, and infinite, then time must be an image of eternity, as also this world is related to that one; and instead of the life yonder, there must be another life belonging to this power of the Soul, called life by a homonym, and instead of intelligible motion a motion of a part of the Soul, instead of sameness, similarity, and permanence, there must be that which does not remain the same but is in changing action, instead of spacelessness and unity an image of unity - the unity in continuity - instead of the infinite and whole that which proceeds to infinity by a continual succession, and instead of a compact whole the whole which by parts is always future. For thus it will imitate the compact and infinite whole, if it wishes always to add to its being. For thus even its being imitates the being of that world.25In this explanation of imitation the emphasis falls on the dissimilarities between the two worlds. In particular the life of the Soul and the unchanging life of eternity can both be called life only homonymously. Aristotle's illustration of homonyms, a man and his portrait, allowed for imitation, for the portrait resembles the man in color, in shadow, in expression, in profile; but Plotinus points out no such similarities between eternity and time - it is all difference. Now this is of importance; perhaps it is of too profound importance for treatment in an article on time, for, if time is in no clear sense an image of eternity, then the more basic similarity of this world to the higher world may also be devoid of meaning. And this would take us far beyond a narrow discussion of time.
There must be some sense in which time is a measure, even though the Aristotelian theory is unacceptable. Plotinus had already made a formal, though unsatisfactory, criticism of Aristotle; here in explaining how time and motion are measures, he meets the Aristotelian position squarely. In fact, chapter twelve makes chapter nine superfluous. The chief faults with the theory that time is the measure of motion are these two: Time cannot be a measure of motion and motion a measure of time in the same sense, though Aristotle made no distinction; and, second, the insistence on motion leaves unexplained how rest may be measured by time.
The first point Plotinus wishes to make is that time is essentially not a measure at all. In Aristotle's eyes the fact that time measures something is an integral part of the definition. Time is counted motion. This is true to such an extent that time would not exist, were there no soul to do the counting. But Plotinus has already said (9, 78-84) that time's existence does not await our counting; and, instead of time's being a measure or unit of motion, it is more true to say that motion measures time. Let him speak for himself:
The interval from one sunrise to the next is equal to an interval of time and since the type of motion on which we depend is uniform, we use it as a measure. But it is a measure of time, for time itself is not a measure. How could time measure anything, and, if it could measure, of what would it say, this is as big as I am? What is this I? Of course, it is that according to which the measuring is done. Therefore time exists in order to measure, but not as a measure. The motion of the universe is measured according to time, and time is not the measure of motion essentially; but being something else first, it will accidentally indicate the quantity of motion. And by taking a single motion in a given time and counting it repeatedly, the notion of a quantity of time past arises. Consequently it is not absurd to say that motion and the celestial revolution measure time after a fashion - insofar as this revolution can indicate the quantity of time by its own quantity - for we cannot grasp or understand temporal quantity in any other way. That which is measured, i.e., made manifest, by the celestial revolution is time; but time is not produced by the revolution-it is made manifest. And thus [time, which Aristotle calls] the measure of motion is that which has been measured by a determinate motion [the revolution], and since it is measured by this, it must be different from it. As measuring, it is one thing; as that which is measured, it is another; for it is measured accidentally. A parallel situation would exist if one should define magnitude as that which is measured by a foot rule without saying what magnitude was in itself. Or it is as if one, unable to define motion because of its limitlessness, should say that it is that which is measured by space. For taking a space that the motion traverses, one might equate the quantity of motion and the quantity of space.26
Time, then, is not essentially a measure, though it measures motion accidentally. More important is the fact that motion measures time with the celestial revolution as the unit. The difference between Aristotle and Plotinus may be expressed, though perhaps in a sharpened form, by saying that for the former time is the measure or unit of motion, while for Plotinus motion is the unit of time (13, 9-10). Aristotle adds that time is measured by motion, but fails to see that this is purely accidental. He ought not to have it both ways; motion and time cannot define each other.
This criticism of Aristotle had been anticipated in chapter nine where Plotinus briefly says time cannot be a number because time is infinite. It was said to be one of the legitimate considerations that chapter because it is based on the notion that anything measured or counted must be finite; and, since time is infinite, it cannot be measured motion.
Further, to measure is not to produce, as Aristotle seems to imply when saying time cannot exist before it is counted, but to make manifest. Therefore the rotation of the heavens is not to be taken as the cause of time. Quite the reverse: The Soul made both time and the sensible universe, put the latter into the former, and therefore, since the sensible universe has no other place except the Soul, it moves in the time that belongs to the Soul (II, 28 ff.).
This clarifies the question of rest also. If the celestial sphere should be conceived to stop and rest, the length of the rest would be measurable if and only if the Soul continued to act. If the Soul should cease its activity, there would be no time - and no world, either. But by rest is ordinarily meant the states of rest of things in nature. These rests are just as measurable as are the motions of things, and while Aristotle made provision for measuring rests (221b7), he erred slightly in reducing such to merely incidental measurements. The measurement of rests should be placed exactly on a line with the measurement of motions. On the other hand, it is obvious that motions call time to our attention more forcibly than rests.27
Further, to measure is not to produce, as Aristotle seems to imply when saying time cannot exist before it is counted, but to make manifest. Therefore the rotation of the heavens is not to be taken as the cause of time. Quite the reverse: The Soul made both time and the sensible universe, put the latter into the former, and therefore, since the sensible universe has no other place except the Soul, it moves in the time that belongs to the Soul (II, 28 ff.).
This clarifies the question of rest also. If the celestial sphere should be conceived to stop and rest, the length of the rest would be measurable if and only if the Soul continued to act. If the Soul should cease its activity, there would be no time - and no world, either. But by rest is ordinarily meant the states of rest of things in nature. These rests are just as measurable as are the motions of things, and while Aristotle made provision for measuring rests (221b7), he erred slightly in reducing such to merely incidental measurements. The measurement of rests should be placed exactly on a line with the measurement of motions. On the other hand, it is obvious that motions call time to our attention more forcibly than rests.27
The preceding quotation with its context also solves the relatively easy problem of the unit of time. If time is to be measured, rather than to measure, and if time cannot measure itself, and if it is impossible to determine time by the Soul alone, obviously a uniform motion must be selected as a unit of time. Plato, as always, was therefore correct in saying that the stars were begotten to manifest time, to mark its divisions, and to make it measurable. Therefore the Soul produced day and night; these give the number two; and from two come all numbers, so that measurement is possible. The diurnal motion of the sun is therefore the unit of time,28 but to define time by that motion is as absurd as to define space or magnitude by a foot rule.
The interest in this question goes beyond the study of Plotinus as an ancient philosopher. Kant faced the same problem, and yet he may not have seen it so clearly as the great Neoplatonist. In opposition to British empiricism Kant argued that time was no discursive concept, but an intuition, a single thing. There is but one time. Or it may be more correct to say that for Kant the idea of time is the idea of a single object. But it remains unfortunately true that there are many human beings, each with an idea of time. Kant fails - so I would hold - to unify these numerous ideas so as really to make one time. Kant is usually credited with many profound passages, even if some are inconsistent with others; but there is one passage whose conclusion, though absolutely essential to his theory, is far too weighty to be supported on the frail scaffolding that underlies it. This section (B 167-169) is that in which he makes impossible a real unity of time, space, and the categories as well. The argument, or should one say the assertion, is directed against any preformation system that would unite all minds and all nature under the plan of the Creator. Because of his rejection of Leibniz' view, involving rejection of any form of theism or pantheism, Kant is left with a pluralistic universe in which each person has his own space, time, and categories. It might be convenient for all these minds to agree, but it is difficult to see that Kant has provided any basis for agreement.
Thus Kant began with time in the individual mind and failed to achieve unity. Plotinus, on the contrary, begins with the unity of time as the life of the Soul and faces the problem of getting it into each individual mind. "Is time then in us also? It is in every such soul and is similarly in all, and all souls are one. Therefore time cannot be broken apart, anymore than eternity can, though contained in all the eternal beings."29
For Plotinus, therefore, there is one time because there is one Soul. This one time is everywhere because the Soul is everywhere in nature as our souls are everywhere in our bodies; and this time is one in all human souls because all souls are one Soul. Plotinus, thus, fairly saves the unity of time, and this, perhaps all but unregenerate pragmatists will concede, is of philosophic importance.
A short postscript relative to the immediately subsequent history may furnish an appropriate conclusion. Neoplatonic history culminates in Proclus. Just prior comes Augustine, who was to dominate Christian thinking for centuries. As it is often said that Christian philosophy in general and Augustine in particular owe much to Neoplatonism, it is of interest to see how Proclus and Augustine viewed the problem of time. Neither of them adopted the exact position of Plotinus. Before Plotinus, Archytas, who stimulated the discussion of time, made time the measure of the universal motion that is the first and immediate and external activity of the Soul. Plotinus and Porphyry located time higher and made it the life of the Soul. From this life comes the motion Archytas had mentioned. Jamblichus places time still higher and makes time the cause that determines the life of the Soul. Proclus goes still further and makes time a god.30
Augustine, far from following this direction, brings us back to Earth again and locates time in created minds. The problem of measuring the past, which no longer exists, and the future, which does not yet exist, is solved by making past and future both present in the mind. Then too Augustine must justify the doctrine of temporal creation. This preoccupation with revealed religion, and the more ordinary philosophic interest which led Augustine to psychological solutions of the problems of time, both indicate that some accounts of Augustine's dependence on Neoplatonism are a little overdrawn.
1. The Philosophical Review, July 1944.
2. La Theorie de Incorporels, 56-57.
3. Mackenna's translation of these lines is amazing. "If the reference is to the Circuit of the heavenly system (it is not strictly continuous of equable, since) the time taken in the return path is not that of the outgoing movement; the one is twice as long as the other: this Movement of the All proceeds, therefore, by two different degrees; the rate of the entire journey is not that of the first half." Aside from the questions of Greek grammar one may ask what sort of astronomy is involved in this translation.
4. IV, iv, 15.
5. Pierre Duhem, Le System du Monde, I, 264ff.
6. III, vii, 8, 24. Mackenna translates this as continuous motion; and Liddell and Scott, 1940, cite this passage as evidence for understanding ομειδης as continuous. Brehier, however, is correct in writing "d'espece identique," as is shown by the in the following illustration, χαι η εν τοπω. For another case in which Liddell and Scott unfortunately depended on Mackenna, compare my note, "A Reference to Plotinus in Liddell and Scott," in The American Journal of Philology, 1944.
7. Mackenna says "subordinate movement (movement of thing of earth)." But these motions were adequately dealt with a few lines above. What Plotinus has in mind now is the various planetary spheres. Then the next section of the argument naturally treats of the outermost sphere.
8. Mackenna simply does not translate lines 31-35; and his condensation of them fails to do justice to the argument.
9. In line 1 βελτιον does not mean plausible as Mackenna tries to interpret it. The fact that motion is continuous does not make this definition more plausible than the theory discussed in the preceding chapter; but it makes measure a better term than number.
10. The problem of irregular motions and of Aristotle's view is complicated by an apparent discrepancy in Aristotle. When defining time, Aristotle thinks of growth and alteration as continuous (223a29-223b1). And if so, they are regular. On the other hand, he holds that alteration is discontinuous; Physics Z, 5, 236a35-b18; Physics H, 3, 248a6-9. If the former statement is accepted, it is difficult to imagine any irregular motion, so that Plotinus' objection does not apply; if the latter view is emphasized, the discussion seems to follow.
11. Constant acceleration of gravity prevents the freely falling body from moving regularly in any finite time; but this type of motion is beyond the scope of both Aristotle's and Plotinus' thought.
12. ο δε χϱονος εοτι το αϱιθμουμενον χαι ουχ ω αϱιθμουμεν, 219b7-8. Compare 220b8ff. ο δε χϱονος αϱιθμος εοτιν ουχ ω αϱιθμουμεν αλλ ο αϱιθμουμενος.
13. Line 20: Brehier translates: "Mais coment cette ligne, si elle progresse avec le mouvement, mesura-t-elle ce qui l'a fait progresser?" Brehier assumes that motion causes time to run along, but the text carries no such hint. It merely means: "how can it measure that with which it runs along?" '?
14. Aλλ αυτη ουνθεουσα πως μετϱησει το ω συνθει 219a14ff.
15. The text is difficult. Plotinus says παϱαχολουθημα means nothing πϱιν ειπειν τι εοτι το παϱαχολουθουν. So far there is no difficulty and the interpretation I have given seems simple. But the next phrase is: εχεινο γαϱ αν ιοως ειη ο χϱονος. How does this explain the objection? Brehier calmly omits this phrase from his translation. Mackenna, seeing in the εχεινο something distinct from το παϱαχολουθημα, translates το παϱαχολουθουν in the πϱιν clause as causative: "we learn nothing from this... until we know what it is that produces this sequential thing; probably the cause and not the result would turn out to be Time." This gives some sense to the εχεινο γαϱ χ.τ.λ., but it puts a strain on the preceding phraseology.
16. δωπς γαϱ αν λεγηται, εν χϱονω λεγεται.
17. III vii 11, 12-45.
18. Brehier simply translates ειϱλασμεθα
19. τουτον may refer grammatically to χοσμον αισθητον or to a supplied χϱονον.
20. III, vi, 12 and 16-18.
21. I, v, 7.
22. III, ii, 17, 1-5; V i 2. Compare III, ii, chapters 2, 14, and 16; and I, i, 8, 15-23.
23. Compare I, v, 7. Time is an image of eternity because it disperses a unity. The Soul attempts to do away with the permanence of its intelligible model.
24. III, vii, 11, 30, should be understood in consonance with the reference to IV, iv, 15 mentioned in section I above.
25. II, 45-59.
26. III, vii, 12, 33-61.
27. 12, 15ff.; and 13, 1ff.
28. Compare VI, v, 11, 14-21.
29. 13, 65-69. This is one passage where Mackenna has a better translation than Brehier, who seems to have followed Duhem, Le Systeme du Monde, I, 248.
30. Compare Pierre Duhem, Le Systeme du Monde, I, 246ff. On page 257 he writes: "La methode constante des Neoplatoniciens, en effet, est celle dont Jamblique vient de nous donner un exemple; elle consiste a transformer en etres reellement distincts et subsistants par eux-memes toutes les notions que notre esprit peut discerner les unes des autres."
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