Full Idea
Democritus appears to rule out from his austere ontology all so-called emergent entities - even mountains and rivers - on the ground that two or more entities can never combine to produce a new one.
Gist of Idea
Democritus denies reality to large objects, because atomic entities can't combine to produce new ones
Source
comment on Democritus (fragments/reports [c.431 BCE]) by José A. Benardete - Metaphysics: the logical approach Ch.24
Book Reference
Benardete,José A.: 'Metaphysics: The Logical Approach' [OUP 1989], p.193