The Impossibility of Motion - Achilles and the Tortoise

There are many things most of us just take for granted as obvious or just plain common sense, and therefore as not worth wasting our time on. Philosophers, however, nit-picking bunch that we are, are insatiably curious, and in our search for some coherent grand theory of everything, usually mange to find trouble instead, of the conceptual kind, although there is also a respectable history of weird philosophers' deaths, which you may find interesting.

When you question what others take as self-evident, you may come to realize that what we take to be real may be anything but. If you can spare 60 seconds, the following animation demonstrates one of Zeno's famous paradoxes of motion proposed to support his mentor Parmenides' thesis that "all is one" and that change is impossible.

According to this paradox,if you think that it is possible for something to move from point A to point B, you've got to be kidding... and you haven't actually "thought" anything...

And for a more comprehensive introduction to, and analysis of, Zeno's paradoxes, check out the article on the Stanford Encyclopedia of Philosophy.