Site Map


by David Simpson (the Internet Encyclopedia of Philosophy)


The Epicurean system consists of three linked components: Physics, Canonic, and Ethics. These three elements are designed to be interdependent, each one supposedly uniting with and reinforcing the other two. (To cite just one example, Epicurus’ physics supposedly validates both the existence of free will and the fact that the soul disintegrates with the body, ideas that are crucial to Epicurean ethics. The canonic claims to validate the authority and reliability of sensation, which in turn serves as a basis for Epicurean physical theories and ethical views relating to pleasure and pain.) In actual fact, however, the three components are quite separable, and it is certainly possible, for example, to accept Epicurus’ ethical doctrines while entirely denying his canonic teachings and physics.


One of the great achievements of the scientific imagination, the Epicurean cosmos is based on three fundamental principles: materialism, mechanism, and atomism. According to Epicurus the universe covers an infinitude of space and consists entirely of matter and void. For the most part the philosopher upholds Democritus’ theory that all matter is composed of imperishable atoms, tiny indivisible particles that can neither be created or destroyed. He also shares Democritus’ view that the atoms are infinite in number and homogenous in substance, while differing in shape and size. However, whereas Democritus held that the number of atomic sizes and shapes is infinite, Epicurus argued that their number, while large, is nevertheless finite. (As Lucretius notes, if atoms could be any size, some would be visible, and possibly even immense.) As for atomic motion, Democritus had claimed that the atoms move in straight lines in all directions and always in accordance with the iron laws of "necessity" (anangke). Epicurus, on the other hand, contends that their natural motion is to travel straight downwards at a uniform high velocity. At random and unpredictable moments, moreover, they deviate ever so slightly from their regular course, their resulting collisions thus occurring not by strict necessity but always with some element of chance. This theory of atomic "swerve" or clinamen is a crucial feature of the Epicurean world-view, providing (so Lucretius and other adherents believed) a firm physical foundation supporting the existence of free will.

Armed with these basic principles, Epicurus is able to explain the universe as an ongoing cosmic event – a never-ending binding and unbinding of atoms resulting in the gradual emergence of entire new worlds and the gradual disintegration of old ones. Our world, our bodies, our minds are but atoms in motion. They did not occur because of some purpose or final cause. Nor were they created by some god for our special use and benefit. They simply happened, more or less randomly and entirely naturally, through the effective operation of immutable and eternal physical laws.

Here it should be noted that Epicurus is a materialist, not an atheist. Although he argues that not only our earth and all its life forms, but also all human civilizations and arts came into being and evolved without any aid or sponsorship from the gods, he does not deny their existence. He merely denies that they have any knowledge of or interest in human affairs. They live on immune to destruction in their perfectly compounded material bodies in the serene and cloudless spaces between the worlds (intermundia), perfectly oblivious of human anxieties and cares. Lucretius imagines that Epicurus rivaled them in their divine tranquility.


The so-called canonic teachings of Epicurus (from the Greek kanon, "rule") include his epistemological theories and especially his theories of sensation and perception. In certain respects, these theories represent Epicurus’ thought at its most original and prescient – and in one or two instances at its most fanciful and absurd.

The central principle of the canonic is that our sense data provide a true and accurate picture of external reality. Sensation is the ultimate source and criterion of truth, and its testimony is incontrovertible. Epicurus considered the reliability of the senses a bulwark of his philosophy, and Lucretius refers to trust in sensation as a "holdfast," describing it as the only thing preventing our slide into the abyss of skepticism (4. 502-512).

But if our sensory input is always true and dependable, how are we to account for hallucinations, fantasies, dreams, delusions, and other forms of perceptual error? According to Epicurus, such errors are always due to some higher mental process. They arise, for example, when we apply judgment or reasoning or some confused product of memory to the actual data presented to us by sensation. As Lucretius remarks, we deceive ourselves because we tend to "see some things with our mind that have not been seen by the senses":

For nothing is harder than to distinguish the real things of sense
From those doubtful versions of them that the mind readily supplies. (4. 466-468.)
Epicurus’ theory of sensory perception is consistent with and follows from his materialism and atomism. Like Democritus, he postulates that external objects send off emanations or "idols" (eidola) of themselves that travel through the air and impinge upon our senses. In effect, these subtle atomic images or films imprint themselves on the senses, leaving behind trace versions of the external world (auditory and olfactory as well as visual) that can be apprehended and stored in memory. Once again, perceptual errors can occur in this process, but not because of any inherent problem with sensation itself. Instead, mistakes arise due either to the contamination of the "idols" by other atoms or because of the "false opinions" that we ourselves, through defects in our higher mental operations, introduce.

In short, unless it is distorted by some form of external "noise" or by some processing error attributable to reason, all information conveyed through the senses is true. This is Epicurus’ core canonic teaching. Unfortunately, this belief in the infallibility of sense perception and the unreliability of logic and reason led him and his followers (including Lucretius) into a number of strange conclusions – such as the absurd claim that the sun, moon, and stars are exactly the size and shape that they appear to be to our naked eye. Thus (as strict Epicurean doctrine would have it) the moon truly is a small, silver disc, the sun is a slightly larger golden fire, and the stars are but tiny points of light.


Epicurus’ ethics represents the true goal and raison d’etre of his philosophical mission, the capstone atop the impressive (though hardly flawless) pillars of his physics and epistemology. Like Socrates, he considered moral questions (What is virtue? What is happiness?) rather than cosmological speculations to be the ultimate concerns of philosophical inquiry.

As mentioned earlier, it is possible to accept one component of the Epicurean system without necessarily subscribing to the others. But from Epicurus’ (and Lucretius’) point of view, it is the ethical component that is of vital importance.

As many commentators have noted, the term "Epicure" (in the sense of a self-indulgent bon vivant or luxurious pleasure-seeker) is entirely out of place when applied to Epicureanism in general and to its founder in particular. By all accounts, Epicurus’ own living habits were virtually Spartan, and it is said that he attracted many of his disciples more by his solid character and agreeable temper than by his philosophical arguments. His moral philosophy is a form of hedonism, meaning that it is a system based on the pursuit of pleasure (Gr. 'edone??? which it identifies as the greatest good. But Epicurean hedonism is hardly synonymous with sensual extravagance; nor is it a matter (in St. Paul’s disparaging terms) of "let us eat and drink; for tomorrow we die." It is instead a system that requires severe self-denial and moral discipline. For Epicurus places a much greater emphasis on the avoidance of pain than on the pursuit of pleasure, and he favors intellectual pleasures (which are long-lasting and never cloying) over physical ones (which are short-lived and lead to excess). As for self-indulgence, he argued that it is better to abstain from coarse or trivial pleasures if they prevent our enjoyment of richer, more satisfying ones.

In Epicurean ethics physical pain is the great enemy of happiness and is to be avoided in almost all cases. Mental anguish is even more threatening and potentially debilitating. It follows that the fear of death – and especially the superstitious belief in an after-life of eternal torment – can be particularly devastating source of anxiety and take a terrible toll on humanity, which is why Epicurus sets out so determinedly to crush it.


Return to Table of Contents