 Although human beings, like everything else, are composed of atoms that move according to their fixed laws, our actions are not wholly predetermined — rather than entertain such a paralyzing doctrine, Epicurus says, it would be better to believe in the old myths, for all their perversities (LM 134). What enables us to wrest liberty from a mechanistic universe is the existence of a certain randomness in the motion of atoms, that takes the form of a minute swerve in their forward course (evidence for this doctrine derives chiefly from later sources, including Lucretius and Cicero). It is not entirely clear how the swerve operates: it may involve a small angle of deviation from the original path, or else a slight shift sideways, perhaps by a single minimum, with no change in direction. The idea of such a minute veering, said to occur at no determinate time or place, is less strange in the modern age of quantum physics than it was in Epicurus’ time, and it gave rise to mocking critiques. More problematic today is how the swerve might explain freedom of will — if indeed Epicurus’ idea of the will was like our own. It did, at all events, introduce an indeterminacy into the universe, and if soul atoms, thanks to their fineness, were more susceptible to the effects of such deviations than coarser matter, the swerve could at least represent a breach in any strict predestination of human behavior. And this might have been enough for Epicurus’ purposes: he may not have invoked the swerve in order to explain voluntary action (claiming that it is action deriving, immediately or ultimately, from a swerve or some swerves of the soul’s atoms). He may have wished merely to establish the possibility of action not deriving from the positions of the soul’s constituent atoms at any time plus the effects of collisions among them resulting from their given movements at that time. According to Lucretius (2.225–50), the swerve was also put to use to solve a cosmological problem: if at some (as it were) initial moment all atoms were moving uniformly in a single direction (downward) at the same speed, it is impossible to conceive how the process of atomic collisions could have begun, save by some such device. This seems a curious idea: given that time, like space, was infinite according to Epicurus, he need not have imagined a time prior to collisions. Just possibly the tendency of atoms to emerge from collisions in a preferred direction (by definition “down”) might lead over time to local regions of parallel motion, and the swerve could serve to reintroduce contact among them. In any event, Epicurus may have thought of atoms moving in some uniform direction rather than in diverse ones as a default position for physical theory (because of the simplicity of that hypothesis); thus he may have felt the need to explain how the diversity of the atoms’ motions could have arisen.