Potential and actual infinity? Doesn't the concept encompass both?
Well, now, sure. Thing is, the Greeks* were kind of skeeved by this whole idea of, say, there being as many numbers between 0 and 1 as there are on the entire number line. Understandably. I think potential and actual infinity was pretty much Aristotle's way of addressing Zeno's paradoxes -- like, there's no end to how small you can cut up an interval of time (potential infinity), but that doesn't mean that there's actually an infinite number of tiny bits of time in an instant (actual infinity). If you see what I mean.
(* Ancient Greeks. I make no claims about Raq's neighbors. For that matter, it may be that your regular everyday amphora-maker was totally cool with the idea of the part being as large as the whole, and it's really only the well-known ancient Greek philosophers who couldn't manage it.)