He taught that people should act ethically not because the gods punish or reward them for their actions but because, due to the power of guilt, amoral behavior would inevitably lead to remorse weighing on their consciences and as a result, they would be prevented from attaining ataraxia.

His influence grew considerably during and after the Enlightenment, profoundly impacting the ideas of major thinkers, including John Locke, Thomas Jefferson, Jeremy Bentham, and Karl Marx.

[20] Epicurus's epistemology also bears an unacknowledged debt to the later writings of Aristotle (384–322 BC), who rejected the Platonic idea of hypostatic Reason and instead relied on nature and empirical evidence for knowledge about the universe.

[16] During Epicurus's formative years, Greek knowledge about the rest of the world was rapidly expanding due to the Hellenization of the Near East and the rise of Hellenistic kingdoms.

[24] Although later texts, such as the writings of the first-century BC Roman orator Cicero, portray Epicureanism and Stoicism as rivals,[24] this rivalry seems to have only emerged after Epicurus's death.

[27] An inscription on the gate to The Garden is recorded by Seneca the Younger in epistle XXI of Epistulae morales ad Lucilium: "Stranger, here you will do well to tarry; here our highest good is pleasure.

[35] Possible insights into Epicurus's death may be offered by the extremely brief Epistle to Idomeneus, included by Diogenes Laërtius in Book X of his Lives and Opinions of Eminent Philosophers.

[37] The authenticity of this letter is uncertain and it may be a later pro-Epicurean forgery intended to paint an admirable portrait of the philosopher to counter the large number of forged epistles in Epicurus's name portraying him unfavorably.

[60][61] In his Letter to Menoeceus, Epicurus explains that people seek wealth and power on account of these fears, believing that having more money, prestige, or political clout will save them from death.

[70] The Tetrapharmakos presents a summary of the key points of Epicurean ethics:[71] Although Epicurus has been commonly misunderstood as an advocate of the rampant pursuit of pleasure, he, in fact, maintained that a person can only be happy and free from suffering by living wisely, soberly, and morally.

[63][72][73] He strongly disapproved of raw, excessive sensuality and warned that a person must take into account whether the consequences of his actions will result in suffering,[63][74][64][73] writing, "the pleasant life is produced not by a string of drinking bouts and revelries, nor by the enjoyment of boys and women, nor by fish and the other items on an expensive menu, but by sober reasoning.

"[90] Like Democritus before him, Epicurus taught that all matter is entirely made of extremely tiny particles called "atoms" (Ancient Greek: ἄτομος; atomos, meaning "indivisible").

[101] Epicurus's reason for introducing this doctrine was because he wanted to preserve the concepts of free will and ethical responsibility while still maintaining the deterministic physical model of atomism.

[102] Lucretius describes it, saying, "It is this slight deviation of primal bodies, at indeterminate times and places, which keeps the mind as such from experiencing an inner compulsion in doing everything it does and from being forced to endure and suffer like a captive in chains.

"[107] Epicurus maintained that he and his followers knew that the gods exist because "our knowledge of them is a matter of clear and distinct perception", meaning that people can empirically sense their presences.

[108] Epicurus rejected the conventional Greek view of the gods as anthropomorphic beings who walked the earth like ordinary people, fathered illegitimate offspring with mortals, and pursued personal feuds.

[112] In this poem, Lucretius declares that popular religious practices not only do not instill virtue, but rather result in "misdeeds both wicked and ungodly", citing the mythical sacrifice of Iphigenia as an example.

"[119] The overwhelming majority of surviving Greek and Roman sources are vehemently negative towards Epicureanism[123] and, according to Pamela Gordon, they routinely depict Epicurus himself as "monstrous or laughable".

[131] During the Middle Ages, Epicurus was remembered by the educated as a philosopher,[131] but he frequently appeared in popular culture as a gatekeeper to the Garden of Delights, the "proprietor of the kitchen, the tavern, and the brothel.

[131] Epicurus and his followers appear in Dante Alighieri's Inferno in the Sixth Circle of Hell, where they are imprisoned in flaming coffins for having believed that the soul dies with the body.

[138] In the seventeenth century, the French Catholic priest and scholar Pierre Gassendi (1592–1655) sought to dislodge Aristotelianism from its position of the highest dogma by presenting Epicureanism as a better and more rational alternative.

[138] For instance, Lucy Hutchinson (1620–1681), the first translator of Lucretius's On the Nature of Things into English, railed against Epicurus as "a lunatic dog" who formulated "ridiculous, impious, execrable doctrines".

[138] His next work Physiologia Epicuro-Gassendo-Charletoniana, or a Fabrick of Science Natural, upon a Hypothesis of Atoms, Founded by Epicurus, Repaired by Petrus Gassendus, and Augmented by Walter Charleton (1654) emphasized this idea.

[139] By the end of the seventeenth century, Epicurean atomism was widely accepted by members of the English scientific community as the best model for explaining the physical world,[140] but it had been modified so greatly that Epicurus was no longer seen as its original parent.

[140] The Anglican bishop Joseph Butler's anti-Epicurean polemics in his Fifteen Sermons Preached at the Rolls Chapel (1726) and Analogy of Religion (1736) set the tune for what most orthodox Christians believed about Epicureanism for the remainder of the eighteenth and nineteenth centuries.

[140] In 1685, Sir William Temple (1628–1699) abandoned a promising career as a diplomat and instead retired to his garden, devoting himself to writing essays on Epicurus's moral teachings.

[140] That same year, John Dryden translated the celebrated lines from Book II of Lucretius's On the Nature of Things: "'Tis pleasant, safely to behold from shore / The rowling ship, and hear the Tempest roar.

[144] Marx viewed Democritus as a rationalist skeptic, whose epistemology was inherently contradictory, but saw Epicurus as a dogmatic empiricist, whose worldview is internally consistent and practically applicable.

[146] Friedrich Nietzsche once noted: "Even today many educated people think that the victory of Christianity over Greek philosophy is a proof of the superior truth of the former – although in this case it was only the coarser and more violent that conquered the more spiritual and delicate.

"[147] Academic interest in Epicurus and other Hellenistic philosophers increased over the course of the late twentieth and early twenty-first centuries, with an unprecedented number of monographs, articles, abstracts, and conference papers being published on the subject.