Full Idea
Democritus erred when he said that the atoms alone exist in truth among realities, but everything else is convention; for then, far from discovering the truth, we shall not even be able to live, since we shall avoid neither fire nor wounds.
Gist of Idea
If only atoms are real and the rest is convention, we wouldn't bother to avoid pain
Source
report of Democritus (fragments/reports [c.431 BCE]) by Diogenes (Oen) - fragments/reports F2 7
Book Reference
Plutarch: 'Moralia - vol 14', ed/tr. Einarson,B. /De Lacy P.H. [Harvard Loeb 1967], p.158
A Reaction
The point is that we have to treat pain as a reality, not just as a convention. I suspect that Diogenes is making the same mistake made by modern attackers of 'eliminativism'. It is all about identity and reduction and levels of reality…