Zeno

Many people are familiar with Zeno's paradox, though probably not in the form presented by XKCD:

(If you aren't familiar with it or need a refresher, just follow the link above.)

Perhaps this is widely known, but I only recently discovered what the point of Zeno's paradox was: he was trying to prove that motion is impossible. Nothing ever moves and nothing ever changes.

This probably sounds absurd, but it was the basis of a philosophical school of which Zeno was part. Zeno created a number of paradoxes, all of which were meant to demonstrate that if the idea that nothing ever moves or changes is absurd, well then it is no more absurd than the idea that things do move and do change. If motion was possible, you would end up, for instance, with Zeno's never-ending race.

This is just another demonstration that many famous philosophical ideas are often remembered now for reasons very different from the reason for which they were first put forth.

(Insight gleaned from Anthony Gottlieb's excellent The Dream of Reason).