Full Idea
By posing the problem of determinism, Epicurus became arguably the first philosopher to recognise the philosophical centrality of what we call the Free Will Question. His strongly libertarian approach is strongly contrasted with Stoic determinism.
Gist of Idea
Epicurus was the first to see the free will problem, and he was a libertarian
Source
report of Epicurus (fragments/reports [c.289 BCE]) by AA Long / DN Sedley - Hellenic Philosophers commentary
Book Reference
'The Hellenistic Philosophers:Vol.1 translations', ed/tr. Long,A. /Sedley,D. [CUP 1987], p.107
A Reaction
Epicurus introduced the rather dubious 'swerve' of the atoms to make room for free will. It seems to me more consistent to stick with the determinism of Democritus. Zeno became a determinist in reaction to Epicurus.