The now ‘in one sense is always the same, in another it is not the same’ (Physics IV 11, 219b30-31)
Aristotle presents a number of puzzles about time. One of these has to do with whether the ‘now’ is always distinct at different times or always remains the same. For, “it is not easy to see whether the now, which appears to divide the past from the future, remains one and the same on all occasions, or is a distinct thing on distinct ones” (Physics IV.10, 218a). The answer to this puzzle will be that there is a sense in which the now is “in a way the same and in a way not the same.” The explanation is that “insofar as it occurs on different occasions it is distinct…whereas that (whatever it is) by being which the now is [what it is], is the same” (4.11, 219b). What he is getting at is the fact that ‘nows’ are the same insofar as they unite past and future, but different insofar as they unite this or that past and future. This solves the puzzle in IV.10.
The puzzle involves the following dichotomy: either the now is always the same or the now is always distinct (from other nows). Problems with either possibility are presented (IV.10, 218a). If there is always a distinct now on each distinct occasion, then each previous now must have passed away and ceased to be. The question arises as to when a previous now could pass away. It cannot pass away while it still is (it cannot be and not be in the same now). But, then, it cannot pass away in another now because it is impossible for nows (being indivisible) to be contiguous to each other. However, there cannot be only one now because nows are limits and anything that is limited cannot have only one limit. A now is a limit of time and, if we consider a limited amount of time, we realise that an earlier now and a later now are required. As Aristotle will say later, “if the now were not distinct but one and the same, there would not have been time” and if we do not observe a gap between any nows, it appears as if there was no time in between, which leads us to identify the nows as one (IV.11, 218b). Also, if we say that the now is always one and the same now, then a now several thousand years ago will be one and the same with this very now. If all nows are one and the same, then they are simultaneous, and so “nothing will be either before or after anything else” (IV.10, 218a).
In order not to fall into the first puzzle, we must recognise that nows do not pass away insofar as they are nows, but insofar as they were the nows that united the past and future in a previous time, relative to that previous time.[1] And, if we are not to accept that all nows are simultaneous, then there must be a sense in which earlier nows and later nows are different.
Nows are distinct insofar as they are nows of different occasions. Different nows are possible when we have a succession of time and motion. Aristotle compares the now to something that is undergoing spatial motion. For, “what is in spatial movement is distinct by being in distinct places” (IV.11, 219b). The difference between Coriscus in the marketplace and Coriscus in the Lyceum is the difference of him being in those distinct places. But insofar as Coriscus is Coriscus, he remains the same. Likewise, what is a ‘now’ is distinct from another now by being the now of an earlier or later linking of a given past and future. But insofar as each now is a now, there is no difference. A now cannot differ from another now in being a now any more than a horse can differ from another horse by being a horse.
It is true that any now must be what unites the past and future, but that does not tell us which past and which future. If we consider a given point in a line, we consider a certain potential division in that line. If we consider another point further up, then we are considering another potential division further up. Those two points are different, and they are differentiated by their different positions. However, insofar as they are the potential divisions in a line, they are the same. They are both potential divisions in that line. We can compare nows to these points and the line to a stretch of time. If you mark out a potential division in that stretch of time, then you will realise that anything posterior to it is future, relative to it, and anything prior to it is past, relative to it. The difference, of course, is that a line is not a temporal entity but a spatial one. All the line is actual at the same time and all the points are potential divisions of that line at the same time. But time flows on. The past ceases to be and Aristotle insists that time will always go on and always be a principle of the future (IV.13, 222b). When we consider previous ‘nows’, we realise that they are not actually still ‘now.’ What we mean when we call them ‘nows’ is that they were nows at the points we are looking back upon. When they were nows, there was time that was future relative to them, but which is now past relative to us currently.
Because time continuously flows on,[2] we can never actually stop at a ‘now.’ The universe as a whole will always have some future change, and time is a universal measure. So, while we can zoom in and consider the now that terminates a particular limited amount of time that we consider, of a particular change, we should remember that the termination of the change did not freeze all of time. In considering this limited stretch of time, we are marking off either end and zooming in at it, abstracting from past time before the limited stretch of time and future time after it. Yet, of course, whenever some limited stretch of time does finish, time as a whole will still flow on and continue in reality. Ursula Coope emphasises that nows do not actually divide time but are used to ‘mark off’ potential divisions in time. Just as a point “marks the line into two parts but does not actually divide the parts from one another,” so “a now is a potential division in time since it marks the time into two parts, though it does not (and in fact cannot) actually divide the parts from one another.”[3] We are always in the present but we never stop at any indivisible now because time is continuous. Because we never stop at any indivisible now, there is no real paradox of the now ‘passing away.’ The now is always a potential terminus of time. It can be the terminus of a limited stretch of time that we isolate in our minds, but it can never be terminus of all of universal time. Insofar as the now is that point at which the past ends and the future begins, it does not pass away, but it might be said to ‘pass away’ inasmuch as the contents of what counts as past and what counts as future changes. The sense in which nows are distinct is that they are the unifiers of different given pasts and futures. A given now several thousand years ago terminated the past previous to it but was the principle of the future time to come. But the contents of the past and future changes. So, that which unites the past and future changes as to what it unites. The past is always being ‘added to,’ as it were, given the continuousness of time. Indeed, there is also a sense in which the past is always the same but also different. It is always the same, insofar as the past is always the past, but is always different, insofar as what counts as past is constantly being added it.
The past is always past and the future is always yet to come. Because the now is what unites the past and the future, it is therefore always ‘now.’ However, because time is continuous, the past is always being added to and what used to be in the future is now in the past. Therefore, the now is different from all previous nows insofar as the past and future it unites are different from what was past and what was future relative to those previous nows.
[1] That future is no longer future but it was then.
[2] This is based upon the fact that there will always be some future change. Aristotle holds that the physical world is sempiternal and will always continue. There will always be some future change in this physical world from any standpoint in time. But even if, contra-Aristotle, one were to claim that there is a point when all change will permanently cease, then we can still consider the continuous flow of time up until that point. Time is the measure of change with regards to prior and posterior. Insofar as there is the posterior of a change yet to come, there is measurable time up until that point.
[3] Coope, Ursula, Time for Aristotle, OUP 2005, 131
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