But what time really is and under what category it falls, is no more revealed by anything that has come down to us from earlier thinkers than it is by the considerations that have just been urged. For (a) some have identified time with the revolution of the all-embracing heaven, and (b) some with that heavenly sphere itself. But (a) a partial revolution is time just as much as a whole one is, but it is not just as much a revolution; for any finite portion of time is a portion of a revolution, but is not a revolution. Moreover, if there were more universes than one, the re-entrant circumlation of each of them would be time, so that several different times would exist at once. And (b) as to those who declare the heavenly sphere itself to be time, their only reason was that all things are contained "in the celestial sphere" and also take place "in time", which is too childish to be worth reducing to absurdities more obvious than itself.