As regards the investigation of time, Aristotle remarks (Phys. IV. 10, 11, 13) that if time is externally (exoterically, ἐξωτερικῶς) regarded, we are inevitably led to doubt (διαπορῆσαι) whether it has any being whatever, or whether it has bare existence, as feeble (μόλις καὶ ἀμυδρῶς) as if it were only a potentiality. “For one part of it was and is not: another part will be and is not as yet; but of these parts infinite and everlasting (ἀεὶ λαμβανόμενος), time is composed. But it now appears that time, if composed of things that are not, may be incapable of existence. And also as regards everything divisible, if it exists, either some or all of its parts must be. Time is certainly divisible; but some of the parts are past, others are future, and no part is present. For the _now_ is no part, since a part has a measure, and the whole must consist of the parts; but time does not appear to consist of the Now.” That is to say, because the Now is indivisible, it has no quantitative determination which could be measured. “Besides it is not easy to decide whether the Now remains, or always becomes another and another. Again, time is not a movement and change, for movement and change occur in that which is moved and changed, or accompany time in its course; but time is everywhere alike. Besides change is swifter and slower, but time is not. But it is not without change and motion” (which is just the moment of pure negativity in the same) “for when we perceive no change, it appears as if no time had elapsed, as in sleep. Time is hence in motion but not motion itself.” Aristotle defines it thus: “We say that time is, when we perceive the before and after in movement; but these are so distinguished that we apprehend them to be another and another, and conceive that there is something between, as a middle. Now when we understand that the extremes of the conclusion are different from the middle, and the soul says that the Now has two instants, the one prior and the other posterior, then we say that this is time. What is determined through the Now, we call time, and this is the fundamental principle. But when we are sensible of the Now as one, and not as a prior and posterior in motion, nor as the identity of an earlier or later, then there does not appear to us to have been any time, because neither was there any motion.” Tedium is thus ever the same. “Time is hence the number of motion, according to priority and posteriority; it is not motion itself, unless so far as motion has number. We judge of the more or less through number, but of a greater or less motion by time. But we call number that which can be numbered, as well as that with which we number; but time is not the number with which we number, but that which is numbered, and, like motion, always is changing. The Now is, which is the unity of number, and it measures time. The whole of time is the same, for the Now which was is the same” (universality as the Now destroyed) “but in Being it is another. Time thus is through the Now both continuous (συνεχής) and discrete (διῇρηται). It thereby resembles the point, for that also is the continuity of the line and its division, its principle and limit; but the Now is not an enduring point. As continuity of time the Now connects the past and the future, but it likewise divides time in capacity,” the Now is only divisibility and the moments only ideal. “And in as far as it is such, it is always another; but, in as far as it unites, it is ever one and the same. Similarly, in as far as we divide the line, other and yet other points always arise for thought; but in as far as it is one, there is only one point. Thus the Now is both the division of time in capacity, and the limit and union of both” _i.e._ of the prior and posterior. The universally dividing point is only one as actual; but this actual is not permanently one, but ever and again another, so that individuality has universality, as its negativity, within it. “But division and union are the same, and similarly related; however their Notion (τὸ εἶναι)[95] is different.” In one and the same respect the absolute opposite of what was posited is immediately set forth as existent; in space, on the other hand, the moments are not set forth as existent, but in it first appears this being and its motion and contradiction. Thus the identity of the understanding is not a principle with Aristotle, for identity and non-identity to him are one and the same. Because the Now is only now, past and future are different from it, but they are likewise necessarily connected in the Now, which is not without before and after; thus they are in one, and the Now, as their limit, is both their union and their division.