People have always sought the highest Good in life. Epicureanism was one of the philosophical streams that had an important influence on the Western tradition of thought.
This conception stresses that the highest Good in life is pleasure and the highest evil is pain. While maintaining this, it avails of some arguments that it takes from other domains, especially physics (in the ancient sense of this concept).
It starts by assuming that humans are animals, or at least belong to the animal kingdom. Yes, they are superior to other animals by being able to think and to act consciously, but still, they fundamentally are animals.
Unlike Epicureanism, Christianity, for example, admits that man is an animal, but he is not exclusively an animal: he also has a soul that is much more important than his animal part, because the acts of this soul will determine its future condition. Once Christianity postulated the idea that there is an immortal soul — a soul whose destiny depends on its present acts — morality acquired a completely different shape than in other ancient streams of thought.
Epicureanism assumes that the ultimate components of reality are atoms, i.e., the smallest parts of matter that cannot be further divided and that move incessantly in an infinite void. Atoms make up everything: from the inanimate stone to stars and living beings. Everything occurs as a consequence of the chaotic motion of these atoms: this chaotic character is due to the collisions of atoms.
However, over a very long time, the initial chaos transforms into an ordered universe, merely due to a continuous change of the existing structures. This materialist principle is essential for the whole system.
Because humans are nothing else than atoms, they share the condition of the other animals. These, too, are made up of atoms. For an Epicurean, it was self-evident that humans could not be something else, that thinking is not a capacity able to transcend material reality and penetrate into spiritual realms.
Therefore, the behavior of animals could serve as a model for understanding the fundamental traits of the human being: what animals needed, humans would need too, and what those avoided, the latter would also avoid.
In comparison to Epicureanism, Christianity and other religions assumed that to truly understand the man you need a supernatural revelation. Man cannot adequately understand himself without relating himself to supernatural beings. The human being needs to be taught to discover his superior nature, to be ‘initiated.’
On the other hand, Epicureans did not realize that humans cannot comprehend themselves without making use of cultural models concerning other entities: for example, a primitive identifying himself with a totem animal, will consider that his highest happiness lies in the way that totem animal feels satisfaction — which certainly is not true for a more civilized person.
In the human mind, no innate principle can work as a natural mainspring to lead man spontaneously toward the highest Good and let him avoid the highest evil. Epicureans did not see that by being forced to turn to cultural models, the human intellect acknowledges its separate character concerning nature.
As other philosophers argued later, if a man were only nature, his ignorance about wherein the highest Good consists could not exist: nature would have endowed him with a sure instinct to recognize immediately what is best for him and not let him go astray in his quest for the highest good.
However, we might doubt that Epicureans would have been able to discover such an idea. Ancient and traditional philosophy generally assumed continuity between nature and mind. This idea, elaborated first by Plato, was developed by Aristotle, who maintained that truth is the correspondence between human intellect and things.
Only in modernity was this idea abandoned, when Kant considered that such a correspondence is impossible because our senses cannot mirror reality adequately, due to the subjective framework in which these senses operate.
Because of that fundamental unity between man and nature, philosophers had thought that knowledge of the fundamental structures of nature was possible. Thus, when Epicurus and Epicureans in general claimed that the most fundamental animal reaction of seeking pleasure and avoiding pain was a clear indication that the same feature ultimately defined humans too, they assumed a continuity between the animal kingdom and humans.
They assumed that the search for pleasure is something as natural as the human body itself. Also, they overlooked the fact that by considering pleasure the highest Good that all humans must aim at, they transformed pleasure from a bodily reaction and feature into a value, endowing it with normative character: because all animals are searching for pleasure, humans must do the same thing!
Pleasure is here no longer a bodily state, but something that must be permanently sought, a ‘call to action,’ something that is no longer only noticed but also evaluated as being good. They could not have made this shift if they had not assumed that humans must behave like animals, i.e., that they are mere animals and therefore, they must imitate what they see other animals doing.
A pleasant state of body by itself cannot yet be a value. You must become detached from yourself, as it were, in order to weigh if what you feel is right or wrong.
When Epicureans say that only the useful character of a pleasure allows us to distinguish between acceptable pleasures and unacceptable ones, they do not realize that through such a procedure pleasure as such has not yet become a good in itself, i.e., something that should always be chosen at the expense of other things, a value.
You can do this only when you have a criterion that allows you to do it, that is to say when you have a superior item that is postulated beforehand as being good and in relation to which something else can be evaluated as being good too.
Epicureans postulate that nature is nothing else than the movement of atoms. Its simplicity builds the original model of any perfection and any preference. Therefore, everything that aims at perfection, i.e., every value, must try to approximate that model. Atoms are lacking intention; they simply exist.
Thus a good life for Epicureans is a life that is as closely related to nature as possible, as devoid of any addition as possible: a life that is pure sensation as an immediate expression of that initial manifestation of nature.
We might thus formulate the following syllogism: Because 1. pleasure is a state that every living being spontaneously prefers to all other states, and 2. it is a product of nature, which is the highest, the most important being; it follows that pleasure can become a value, i.e., it can transform into a demand — or a norm — to live your life according to what is set as the ultimate existence.
Thus it is not the fact that pleasure is the most intense feeling in humans that makes it a value, but the fact that nature is a mechanical assembly of atoms which requires us to behave like a mechanism and consider as a good what appears as the elementary, yet the most intense and natural sensation, a sensation that is nothing other than a product of the movement of atoms.