Epicurus set up his school, the Garden, in Athens in 306. Only a small percentage of Epicurus' writings have survived, partly because his philosophy became unpopular and was not preserved once the critical reaction to the classical tradition gave way to the resurgence of non-skeptical forms of Platonism and the subsequent rise of Christianity as the dominant intellectual tradition.

Diogenes Laertius (3rd century C.E.) lists the forty-one titles of Epicurus' "best" books (Lives of Eminent Philosophers X.27). None of this work has survived.

What is now known about Epicurus and his philosophy depends primarily on three letters Diogenes Laertius preserves in Book X of his Lives of Eminent Philosophers: Letter to Herodotus (outlines the Epicurean philosophy of nature), Letter to Pythocles (discusses natural phenomena in the sky), and Letter to Menoeceus (outlines the Epicurean position on happiness).

Historical Figures

Epicurus (341-270), founded his school (called the Garden) in 306
Hermarchus, successor to Epicurus as head of the school
Lucretius (c. 99-55), Roman poet and author of On the Nature of Things (which sets out Epicureanism)

Happiness and the Good Life

One of Epicurus's most important contributions is move toward empiricism. From within this new perspective, he came to a significantly different set of conclusions about human beings, their place in reality, and the good life. Epicurus thought that the good life is the life of enlightened moderation and that "contemplation" is not essential to this life.

The good life is enlightened because it includes knowledge of structure of reality necessary to dispel the fears engendered by mythology and superstition. The good life is a life of moderation because extravagant goals, such as having the fanciest foods, are difficult to secure and thus are likely to be a source of frustration.

"There are some people who think that it was on the basis of the unexpected events that happen in the world that we have come to conceive of gods; Democritus too seems to be of this opinion. For, he says, when ancient men saw what happens in the sky, like thunder, lightning, lightning bolts, conjunctions of stars, eclipses of the sun and moon, they became frightened and thought that gods were the causes of these things" (Sextus Empiricus, Against the Mathematicians 9.24).

"For who do you believe is better than a man who has pious opinions about the gods, is fearless about death, has reasoned out the natural goal of life and understands that the limit of good things is easy to achieve completely and easy to provide, and that the limit of bad things either has a short duration or causes little trouble?" (Epicurus, Letter to Menoeceus X.133.)

Epicurus thought that the study of nature would be unnecessary were human beings not prone to worrisome false beliefs about celestial phenomena. If they do not understand the nature of reality, human beings are plagued by fear of the sorts of events described in mythology. They make up threatening stories about natural phenomena they do not understand. They think these phenomena indicate divine mood and that storms and other such phenomena are punishment from the gods. Epicurus thought knowledge of physics contributes to the good life by dispelling the fears enshrined in mythology. He thought that theoretical investigations are useful to correct the unfortunate and all too common tendency of human beings to form certain distressing but false beliefs.

Philodemus, Herculaneum Papyrus, 1005. Discovered at the Villa of the Papyri in Herculaneum.

Epicurus thought that human beings are prone to false beliefs about the gods, death, the availability of good things, and the likelihood of experiencing bad things. Yet, in truth, as Epicurus seems to have said in his fourfold remedy,

"God presents no fears, death no worries, and while good is readily attainable, bad is readily endurable" (Philodemus of Gadara, preserved in Herculaneum Papyrus 1005, 4.10–14).

Epicurus advances this fourfold remedy as a solution to life's most worrying problem. A human being who takes this remedy realizes that there is an easy-to-execute and effective plan for living in a way that is overwhelmingly likely to result in a life in which the pleasure taken in one's circumstances vastly outweighs the pain. This knowledge is a source of immense relief and satisfaction. Because this relief consists in the removal of prior worries, it makes a human being happier than before taking the remedy. In addition, Epicurus the suggestion seems to be that this knowledge is itself a source of immense satisfaction and that this satisfaction is on-going because the knowledge is on-going. The presence of this knowledge ensures that the few bad things that do happen are not nearly disturbing enough to undermine one's overall happiness.

The Contrast with the Classical Tradition of Plato and Aristotle

Given only this much, there can appear to be a significant resemblance between the Epicurean conception of happiness and the conception present in Plato and Aristotle. In Plato, the best existence is the one the soul enjoys in its disincarnate and natural state, fixed in contemplation, free from practical concerns and the need for reason to deal with those concerns. Its existence, in this natural and disincarnate state, is characterized by knowledge of the forms. Aristotle's position is more nuanced. He thinks that contemplation contributes most of all to happiness, but he also thinks that the excellent exercise of reason in practical matters contributes to happiness "secondarily," or in a "secondary way." Since for Epicurus there is immense pleasure in the knowledge that a certain plan for living is both straightforward and likely to result in happiness, one might think that he has a version of the view of happiness one finds in the classical tradition of Plato and Aristotle.

In fact, there is reason to doubt that Epicurus has this sort of view. The evidence is sparse, but it is easy to get the impression that he rejected this way of thinking about happiness and knowledge as part of his rejection of the rationalism of the classical tradition. Epicurus stresses memory in a way that suggests he is more allied with the empiricist tradition Plato and Aristotle rejected (Phaedo 96b, Posterior Analytics II.19.99b, Metaphysics I.1.980a). In his Letter to Herodotus, Epicurus makes memory play an important role with respect to happiness and the good life. He says that "freedom from disturbance ... [involves] a continual remembrance (μνήμην) of the general and most important points [of Epicureanism]" (Diogenes Laertius, Lives of Eminent Philosophers X.82). It is true that he tried to present his doctrines in summary form for easy consumption and retention. It is also true that he uses θεωρία and its cognates, as these are ordinary Greek words. However, the stress he places on memory and the "continual remembrance" of his doctrines suggests that he rejected the rationalism of the prior classical tradition. It suggests that he did not think of the knowledge that contributes to happiness in terms of "contemplation" (θεωρία) and the perfection of reason. The evidence makes the issue difficult to settle conclusively, but it seems that for Epicurus knowledge contributes to happiness in a significantly different way than it does for Plato and Aristotle. The point for him is not that knowledge and contemplation of the structure of reality is itself supremely pleasurable. Rather, the driving idea for Epicurus seems to be that once a human being knows that the "good is readily attainable" and that the "bad is readily endurable," as is proclaimed in the fourfold remedy, he will take great pleasure in thinking about his actions in the various circumstances in which he is likely to find himself in the future. Epicurus seems to say that when a human being thinks about how things might go for him in the future, which is something that a human being does whenever he thinks about what he should do, he is not at all worried or anxious because he knows that "God presents no fears, death no worries, and while good is readily attainable, bad is readily endurable."

Knowledge, Experience, and Reason

Epicurus does not work out his epistemology in much detail in what survives of his writing, but he seems to have thought that having the right beliefs is somehow not a matter of "reason" but really involves nothing more than the cognition involved in "experience." The idea is that knowledge is a matter of perception, memory, and forming beliefs in the right way .

Human beings have perceptions, and these perceptions give rise to various thoughts. Epicurus seems to say that the perceptions themselves are never false and that falsehood is always a matter of accepting the accompanying thoughts uncritically. According to Epicurus, the thoughts should be accepted only if they are confirmed and also are not disconfirmed. Further, he rejects "dialectic as superfluous" (Diogenes Laertius, Lives of Eminent Philosophers X.31). The surviving evidence does not show very clearly just what he had in mind in rejecting dialectic, but his view seems to be that to account for this way of accepting the thoughts occasioned by perception, it is a mistake to appeal to "reason" as this is understood in the rationalist tradition of Plato and Aristotle.

The disagreement between the rationalist conceptions of epistemology and the one Epicurus seems to try to develop is about how to account for the ability to form true beliefs. Epicurus seems to reject "reason" as it is understood in the rationalist tradition and to deny that human beings have a faculty of reason beyond the ordinary ability to be reasonable or rational. Aristotle's view, for example, seems to be that reason first and foremost grasps universals and thinks in accordance with syllogistic logic to deduce their relations of logical consequence and incompatibility. Epicurus seems to reject this conception of reason and to think that his epistemology in terms of perception and confirmation and disconfirmation accounts for the ordinary ability to be reasonable or rational in belief.

(To see some of the import of Epicurus' rejection of "reason" as it is understood in the rationalist tradition, it helps to think about contrast between inference and deduction. To infer Q from P is to believe Q as a result of reflecting on P. Deduction is a matter of tracing out the implications of premises. Deduction can be relevant to inference, but no deduction is an inference.)

"Epicurus' Letter to Herodotus, for instance, is replete with references to memory. He tells us to remember firmly the basic principles of Epicureanism, in fact to memorise them. What is behind these admonitions does not seem to be just the trivial view that if one wants to be an Epicurean one had better remember the basic tenets of Epircureanism, but rather the view that our whole way of thinking is determined by our memory, by what we remember having experienced and what we have committed to memory in the, perhaps wrong, belief that it is the case. It is tempting to think that Epicurus' rejection of dialectic or logic is related to this (see D.L. x.31). As understood by Platonists, Peripatetics or Stoics, dialectic or logic, as we noted earlier, is based on the assumption that there are certain relations between terms or propositions, or rather their counterparts in the world, such that in virtue of these relations certain things follow from, or are excluded by, other things. Dialectic teaches us to see these sometimes complex relations and to reason accordingly. In fact, this is what it is to reason, to argue on the basis of one's adequate or inadequate grasp of, or insight into, these relations. So when Epicurus rejects dialectic, one is inclined to assume that he is rejecting this rationalist view of thought and inference..." (Michael Frede, "An Empiricist View of Knowledge: Memorism," 240-241).

(It is part this same rejection of the rationalism of the classical tradition that preconceptions are memories and that feelings of pleasure and pain are the criteria for choice.)

"For reasoning is a kind of memory combined with things apprehended with the senses" (ὁ γὰρ λογισμὸς μνήμη τίς ἐστι συνθετικὴ τῶν μετ᾽ αἰσθήσιος ληφθέντων) (Hippocrates of Cos, Precepts 1).

Perseus Digital Library: Diogenes Laertius, Lives of Eminent Philosophers
Henry George Liddell, Robert Scott, A Greek-English Lexicon: ἀταραξία