Full Idea
The fact that the mind itself has no internal necessity to determine its every act and compel it to suffer in helpless passivity - this is due to the slight swerve of the atoms at no determinate time or place.
Gist of Idea
The actions of the mind are not determinate and passive, because atoms can swerve
Source
Lucretius (On the Nature of the Universe [c.60 BCE], II.294)
Book Reference
Lucretius: 'On the Nature of the Universe', ed/tr. Latham,Ronald [Penguin 1951], p.68
A Reaction
No one likes this proposal much, but it is very intriguing. The Epicureans had seen a problem, one which doesn't bother me much. If, nowadays, you are a reductive physicalist who believes in free will, you have a philosophical nightmare ahead of you.
Related Idea
Idea 20833 A swerve in the atoms would be unnatural, like scales settling differently for no reason [Chrysippus, by Plutarch]