Full Idea
If everything is infinitely divided, what survives the divisions? Alternatively, division would end at points with no magnitude, in which case bodies are composed of nothing. This is the argument claiming there are atoms of some magnitude.
Gist of Idea
There must be atoms, to avoid the absurdity of infinite division down to nothing
Source
report of Democritus (fragments/reports [c.431 BCE], A048b) by Aristotle - Coming-to-be and Passing-away (Gen/Corr) 316a14-
Book Reference
'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.175