Epicurus, working within an atomist physics inherited from Democritus that was otherwise strictly deterministic, introduced a controversial modification: atoms, in addition to falling through the void, occasionally swerve from their determined path in a small, unpredictable way, and it is this clinamen, this swerve, that Epicurus and his Roman successor Lucretius argued makes room for genuine agency, since without some break in the chain of necessity, human choice would be no more free than a stone's fall. The proposal was widely mocked even in antiquity for seeming to explain freedom by appeal to sheer randomness, which critics pointed out is not obviously any better than strict determinism from the standpoint of responsibility, since an action caused by a random swerve seems no more genuinely up to the agent than one fully determined by prior causes.
Contemporary libertarians such as Robert Kane have tried to answer this randomness objection directly, arguing that indeterminacy need not be mere randomness if it occurs specifically at moments of significant, effortful deliberation, where an agent is genuinely torn between competing reasons, so that the resulting choice, while not determined, is still intelligibly the agent's own rather than a matter of chance imposed on them from outside.