His philosophy advanced the notion that happiness, obtained by the avoidance of physical and emotional pain and the seeking of pleasure (in moderation) was the highest good.
For Epicurus virtues themselves were all purely instrumental goods, valuable solely for the sake of the happiness that they can bring to a person, not for their own sake.
Epicurus maintained that all of the virtues are ultimately forms of prudence, of calculating what is in one's own best interest.
In this, his philosophy goes against the majority of Greek ethical theorists, such as the Stoics who identify happiness with virtue, and Aristotle who identifies happiness with a life of virtuous activity.
Epicurus also taught that the the world consists basically of atoms, uncuttable bits of matter, flying through empty space, and he tried to explain all natural phenomena in atomic terms.
He rejected the existence of Platonic forms and an immaterial soul saying that the gods have no influence on our lives. He felt that we could gain knowledge of the world by relying upon the senses.
Epicurus is one of the first philosophers to put forward a theory of mind which identifies the mind with the brain, and mental processes with neural processes.
His physiology, however, is quite different in that the mind is
identified as an organ that resides in the chest. The common Greek
view was that the chest, not the head, is the seat of the
Although Epicurus' philosophy combined a physics based on atomistic materialism with hedonistic ethics, he insisted that courage, moderation, and the other virtues are needed in order to attain happiness.
He also thought that natural science and philosophy itself are instrumental goods. Natural science in order to give mechanistic explanations of natural phenomena and thus dispel the fear of the gods, and philosophy to help show us the natural limits of our desires and to dispel the fear of death.
One significant consequence of Epicurus' philosophy of mind is that death is annihilation.
According to him, upon death, the container of the body shatters, and the atoms disperse in the air. The atoms are eternal, but the mind made up of these atoms is not, just as other compound bodies cease to exist when the atoms that make them up disperse.
Therefore, since death is a total annihilation we need only live a simple life and seek ways in which we can seek pleasure (in moderation) and avoid physical pain.