I can’t think of a way to define time (or distance, for that matter) entirely without circularity. We can measure it by comparing it to processes with fixed duration, of course, but to actually define in terms of anything that isn’t itself defined in terms of time (such as velocity) seems like an insurmountable problem. I can’t think of a way to prove it can’t be done, however, so I’m keen to see what light Aristotle might shed on the matter. My suspicion, though, is that we’re all in a predicament like that of a certain fictional square who was unsuccessful in retaining the concept of “upward but not northward”. I don’t doubt the true nature of time will be obvious to us when we look at it from the other side of eternity, but we’ll have to content ourselves with treating it as a primitive concept as long as we’re in it.
Reply to “Physics IV.11–14: Aristotle’s definition of time seems to fit distance and degree of change; can it be rescued from this objection?”