Full Idea
What exists does not exist at all more than what does not exist, and both are causes in a similar way for the things that come about.
Gist of Idea
The non-existent exists as much as the existent, because it has causal powers
Source
Democritus (fragments/reports [c.431 BCE], A008), quoted by Simplicius - On Aristotle's 'Physics' p.28.4-27
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.95
A Reaction
[Simplicius actually attributes this to the shadowy Leucippus] You can see the point. If you drive into a pothole, that has considerable causal powers.