One could make a case for Epicurus -- see e.g. Yvain's review of a book about him (and much else). Warning: I have seen it claimed (1) that the book is full of errors and (2) that in any case much of what's there ascribed to Epicurus was in fact borrowed from other earlier thinkers. I do not know enough about Greek philosophy (or the other things about which the book is alleged to be wrong) to adjudicate any of those fights.