  In general, then, in setting such aporiai, Aristotle does not mean to endorse any given endoxon on one side or the other. Rather, he thinks that such considerations present credible puzzles, reflection upon which may steer us towards a defensible understanding of the nature of time. In this way, aporiai bring into sharp relief the issues requiring attention if progress is to be made. Thus, by reflecting upon the aporiai regarding time, we are led immediately to think about duration and divisibility, about quanta and continua, and about a variety of categorial questions. That is, if time exists, then what sort of thing is it?  Is it the sort of thing which exists absolutely and independently?  Or is it rather the sort of thing which, like a surface, depends upon other things for its existence?  When we begin to address these sorts of questions, we also begin to ascertain the sorts of assumptions at play in the endoxa coming down to us regarding the nature of time.   Consequently, when we collect the endoxa and survey them critically, we learn something about our quarry, in this case about the nature of time—and crucially also something about the constellation of concepts which must be refined if we are to make genuine philosophical progress with respect to it. What holds in the case of time, Aristotle implies, holds generally. This is why he characteristically begins a philosophical inquiry by presenting the phainomena, collecting the endoxa, and running through the puzzles to which they give rise. 