Full Idea
There is a free motion in the atoms, which Democritus did not discover, but which Epicurus brought to light, and which consists in a swerve, as he demonstrated on the basis of what is seen to be the case?
Gist of Idea
Epicurus showed that the swerve can give free motion in the atoms
Source
report of Epicurus (fragments/reports [c.289 BCE]) by Diogenes (Oen) - Wall inscription 54.II-III
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.459
A Reaction
I presume the last bit means that we see that we have freedom of choice, and infer the swerve in the atoms as the only possible explanation. The worry for libertarians is, of course, who is in charge of the swerve.