Full Idea
There is no need for void to be the cause of all change, because it is perfectly possible for a plenum to alter qualitatively (which is something Melissus overlooked).
Clarification
'Void' is total emptiness; a 'plenum' is a smooth, continuous background
Gist of Idea
The void is not required for change, because a plenum can alter in quality
Source
comment on Melissus (fragments/reports [c.443 BCE]) by Aristotle - Physics 214a27
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.94
A Reaction
In modern physics this presumably gives us fluctuations in a force field. Motion is like a cat being digested by a python. The atomist claim that emptiness is needed if anything is to move still has intuitive appeal.