This chapter discusses Aristotle’s claim that there is one and the same time for all simultaneous changes. Aristotle thinks that changes are simultaneous just in case they are bounded by one and the same pair of nows. He does not give a reductive account of simultaneity (that is, he does not explain in virtue of what different changes are bounded by the same pair of nows), but he does insist that any one now divides all the changes that are going on at it. It is argued that he insists on this because he has a certain view about time’s universality: he thinks that time must be an order within which any change, or change part, is related to any other. Aristotle draws a comparison between the fact that the same time is the time of many different changes, and the fact that the same number is the number of different groups (for instance, of seven dogs and seven horses). Based on an earlier account of Aristotle’s definition of time, the comparison he is drawing here is explained.
Keywords: simultaneous, change, nows, number, order, universality