Full Idea
Zeno's so-called 'Achilles' claims that the slowest runner will never be caught by the fastest runner, because the one behind has first to reach the point from which the one in front started, and so the slower one is bound always to be in front.
Clarification
'Achilles' was famous for his speed
Gist of Idea
The fast runner must always reach the point from which the slower runner started
Source
report of Zeno (Elea) (fragments/reports [c.450 BCE]) by Aristotle - Physics 239b14
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.161
A Reaction
The point is that the slower runner will always have moved on when the faster runner catches up with the starting point. We must understand how humble the early Greeks felt when they confronted arguments like this. It was like a divine revelation.