From this explanation we may infer that, as each point, or primitive element, of matter has its own now, one in its absolute reality, but manifold in its mode of being, there are in nature as many nows describing distinct lines of time as there are material points in movement. Accordingly, there are as many particular times as there are elements moving in space. The proposition that in time there is only unum instans in re is, therefore, to be limited to the particular time of one and the same subject of motion. S. Thomas did not think of this limitation, because he believed, according to the old astronomical theory, that the movement of the primum mobile—that is, of the supreme sphere—was the natural measure of time; and for this reason he thought that, as the first movement was one, time also was one, and constituted the common measure of all simultaneous movements.[83] But the truth is that there must be as many distinct particular times as there are things actually moving. This is a manifest consequence of the doctrine which assimilates a flowing now to a point describing a line. For as every point in movement describes a distinct line in space, so also must the absolute now of every distinct being describe by its flowing a distinct line of time.
The general time, which we regard as one successive duration, is the duration of the movement from the beginning of the world to our day, conceived in the abstract—that is, without reference to the particular beings concerned in the movement. Time, when thus conceived, is a mere abstraction; whereas the particular times of particular movements are concrete in their continuous extension, notwithstanding their being represented by abstract numbers. If we knew of any special body created and put in movement before any other body, we might regard it as primum mobile, and take its movement, if uniform, as the natural measure or standard of general time; but as we know of no such particular body, and as we have reason to believe that the creation of all matter was made in one and the same moment, we are led to admit an exceedingly great multitude of prima mobilia, every one of which was from the beginning of time the subject of duration. It is clear that we cannot reduce their distinct durations to one general duration, except by making abstraction of all particular subjects, and considering movement in the abstract.
Nevertheless, as we inhabit the earth, we usually restrict our consideration of time to those periodical intervals of duration which correspond to the periodical movements we witness in, or from, our planet; and thus we take the duration of the diurnal or of the orbital movement of the earth as our standard for the measure of time. If other planets are inhabited by rational beings, it is obvious that their time will be measured by other standards, as their diurnal and orbital movements differ from those of our earth.
To the doctrine that time is evolved by the flowing of a single instant, S. Thomas adds an important remark to the effect that the now of contingent things should not be confounded with the now of eternity. He proposes to himself the following objection: “To stand and to move are not essential differences, but only different manners of being. But the now of eternity is standing, and the now of time is moving. The one, therefore, seems to differ from the other in nothing but in the manner of being. Hence the now of time would be substantially the same as the now of eternity, which is absurd.”[84]
S. Thomas replies: “This cannot be true, according to our doctrine; for we have seen that eternity and time differ essentially. Moreover, when of two things the one depends on the other as an effect from a cause, the two things essentially differ; but the now of eternity (which does not really differ from eternity itself) is the cause of time and of the now of time; therefore the now of time and the now of eternity are essentially different. Furthermore, the now of time unites the past with the future, which the now of eternity does not do; for in eternity there is no past and no future, because eternity is all together. Nor has the objection any force. That to stand and to move do not constitute an essential difference is true of those things which are liable both to stand and to move; but that which always stands without possibility of moving differs essentially from that which always moves without the possibility of standing. And this is the case with the now of eternity on the one hand, and the now of time on the other.”[85]
Beginning of time.—Here the question arises whether time must have had a beginning. Those who believe that the world could have been created ab æterno will answer that time could have existed without a beginning. But we are convinced that the world could not be created ab æterno; and therefore we maintain that time must have begun.
Our argument is drawn from the contingency of all things created.
The duration of a contingent being cannot be without a beginning; for the contingent being itself must have had a beginning. In fact, as that cannot be annihilated which has never been in existence, so that cannot be educed from nothing which has never been nothing. It is therefore necessary to admit that every creature had a beginning of its existence, and consequently of its duration also; for nothing endures but inasmuch as it exists.
Nor can this argument be evaded by saying that a contingent being may have initium naturæ, without having initium temporis. This distinction, though suggested and employed by S. Thomas, has no foundation, because the beginning of the created nature is the beginning also of its duration; and he who concedes that there must be an initium naturæ cannot consistently deny the initium temporis. In fact, no contingent being can be said to have been created, if there was no instant in which it was created; in other terms, every creature must be traced to the now of its creation. But the now of its creation is the beginning of its duration no less than of its existence. Surely, whatever has a first now has a beginning of duration; but every creature has its first now—viz., the now of its creation; therefore every creature has a beginning of duration. That the now of creation is the first now is self-evident; for the now of creation is that point of duration in which the passage is made from not being to being; and therefore it marks the beginning of the existence of the created being. And since we cannot say that the duration of the created being preceded its existence, we are bound to conclude that the now of its creation is the beginning of its duration as well as of its existence.
Some will object that we assume what is to be proved—viz., the very now of creation. For, if the world had been created ab æterno, no now of creation could be pointed out. To this we answer that the now of creation, whether we can point it out determinately or not, must always be admitted. To suppress it, is to suppress creation. For, if we assume that a thing had no now of creation, we are compelled to deny that such a thing has ever been created. In other terms, if anything has no beginning of duration, it was always in act, it never lacked actual existence, and it never passed from non-existence to actual existence—that is, it is no creature at all; for to be a creature is to have passed from non-existence to actual existence. And thus we must conclude that to create is to make a beginning of time.