Full Idea
Democritus and Leucippus say that there are only three differences - in shape, arrangement and position.
Gist of Idea
Atomists say there are only three differences - in shape, arrangement and position
Source
report of Democritus (fragments/reports [c.431 BCE], A006) by Aristotle - Metaphysics 0985b15
Book Reference
'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.172