Given that time is by definition something countable, the question naturally arises whether its existence depends on the existence of beings, like ourselves, who can count it. Aristotle raises this question towards the end of his discussion. Someone might be puzzled, he says, about whether there could be time if there were no ensouled beings. He presents an argument that there could not be. The argument is that since time is a kind of number, it is necessarily countable. As such, it can only exist in a world in which there are beings that can count. Since the only beings that can count are beings that have intellective souls, there can only be time in a world in which there are such beings. He goes on to point out that this argument gives us no reason to think that change depends on the soul, since change, though it is closely connected to time, is not something that is necessarily countable: Someone might raise the puzzle whether if there were no soul there would be time or not. For if it is impossible for there to be something to do the counting, it is impossible also that anything should be countable, so that it is clear that there will not be number. For number is either the counted or the countable. But if nothing else has the nature to count than soul (and in the soul, the intellect), it is impossible for there to be time if there is no soul, except that there could be that, whatever it is, by being which time is (touto ho pote on estin ho chronos), for example, if it is possible for there to be change without soul. The before and after are in change and time is these in so far as they are countable.
We are already familiar with Aristotle’s view that time is necessarily countable. But nevertheless the argument he presents here is puzzling. Why should we accept, for instance, that something countable could only exist in a world in which there were beings able to count? Does Aristotle himself really believe this? Time, as we have seen, is the universal before and after order within which all changes are arranged. Does Aristotle really think that, in the absence of beings able to count, changes would not be arranged in such an order? Still more puzzling is the suggestion that time depends on the soul in a way in which change does not. This seems to imply that there could be a world in which there was change but no time. But Aristotle has already argued that there can be no change without time. He says that ‘it is manifest that every alteration and every changing thing is in time’
Aristotle says that if there were no ensouled beings, there could be no time, but there might nevertheless be change. But he also thinks that there can be no change without time. The key to understanding how these views can be consistent lies in the interpretation of the two counterfactuals: if there were no souls, there would be no time; if there were no souls, there might be changes. For a modern reader, it is natural to read these using the language of possible worlds: in any possible world in which there are no ensouled beings, there is no time; in some of the possible worlds in which there are no ensouled beings, there is change. If this is how we are to understand the counterfactuals, then they straightforwardly imply that there are possible worlds in which there is change but no time. A clue that this is not the right way to understand them is that Aristotle has the (to us rather strange) view that it is impossible for there to be a world without ensouled beings. He thinks that there always have been and will be beings with souls, and that this implies that it is necessary that there are such beings. Thus, when he asks whether there could be time or change in a world without ensouled beings, he is not envisioning a way the world might have been, and asking whether there would be time or change in a world like that. How then should we understand the claim that in a world without ensouled beings there might be change but no time? It is, I think, a claim about the essential natures of time and of change. On Aristotle’s view, the relation between time and the soul is importantly different from the relation between change and the soul. Since time, change, and the soul all exist in every possible world, this difference cannot be captured by talk of what is true in other possible worlds. The difference is this. The nature of time itself implies that time cannot exist in the absence of ensouled beings. On the other hand, it does not follow simply from the nature of change that there could not be change without time, and it also does not follow from the nature of change that change could not exist in the absence of ensouled beings. The nature of a thing is expressed in its definition. Aristotle defines time as ‘a number of change in respect of the before and after’. From this definition, it follows that time could not exist in the absence of ensouled beings. He defines change in terms of potentiality. This definition alone does not imply that change could only exist in a world in which there were such beings. Note that for all I have said, Aristotle might hold that there is some other reason to think that there can only be change if there are souls. He is very noncommittal about whether in a world without souls there could in fact be change. He says only: ‘for example, if it is possible for there to be change without soul’ . If my interpretation is right, it is not surprising that he feels no need here to settle whether or not this really is possible. For although he asks what would be true if there were no ensouled beings, his primary interest is not in exploring what the world would be like if, per impossible, there were no such beings; he is simply using this question as a device by which to clarify certain facts about the relation between the nature of change and the nature of time.