Epicurus (b. c. 341–d. 271 bce) was one of the most influential philosophers of the Hellenistic period, the two centuries or so following the death of Alexander the Great in 323 bce. Epicureanism, alongside Stoicism and Academic Skepticism, was one of the predominant systems of thought competing for the allegiance of people in the Greek- and Latin-speaking world, and communities of Epicureans flourished for centuries following Epicurus’s death. Epicurus revived the atomism of the pre-Socratics Leucippus and Democritus, where everything is ultimately the result of indivisible particles interacting in empty space. However, he modified their atomism by adding weight as a property of atoms as well as a tiny, indeterministic “swerve” to the side that is supposed to account for atomic collisions and to allow for human freedom. Epicurus said that the workings of the world are not due to any divine purpose or plan and that we can explain why organisms operate as they do without recourse to biological functions. Excluding the gods from meddling with the world liberates us from fearing them. Furthermore, the mind is a bodily organ that allows us to think and live, instead of being some immaterial animating principle that can move from body to body. And so, death is annihilation. The realization that death is annihilation should free us from the fear of death: annihilation is simply nothingness, and because after our deaths we do not exist, our death cannot be good or bad for us. Epicurus thought that skepticism about the reliability of the senses was self-refuting and practically disastrous. To avoid such skepticism, he affirmed (contra Democritus) that sensible qualities such as color and taste are genuine properties of bodies, and he even said that all sensations are true. On the basis of these sensations, we can come to a correct understanding of how the world works. In ethics, Epicurus affirmed egoistic hedonism (contra Plato and Aristotle); thus, he affirmed that only my own pleasure is intrinsically good for me. However, this does not license reckless dissipation. Freedom from bodily distress and mental turmoil is by itself pleasant—in fact, the limits of pleasure for us. To attain a trouble-free and tranquil life, we must moderate our desires, cultivate the virtues, live justly, and acquire a circle of trustworthy friends. The wise person will even worship the gods, correctly conceived—not as meddling and jealous world-managers but as exemplars of human blessedness whom we need not fear.