Stoic philosophy was founded in Athens in the third century BC by Zeno of Citium and reached the peak of its popularity among the upper classes of Rome during the first century BC and the first century AD. It was influential throughout the Greco-Roman world until at least AD 200. It was inspired by the teaching of Socrates and Diogenes of Sinope. It stressed duty and held that, through reason, mankind can come to regard the universe as governed by fate and, despite appearances, as fundamentally rational, and that, in regulating one's life, one can emulate the grandeur of the calm and order of the universe by learning to accept events with a stern and tranquil mind and to achieve a lofty moral worth. Its teachings have been transmitted to later generations largely through the surviving books of Cicero and the Roman Stoics Seneca, Epictetus, and Marcus Aurelius.
The Stoic view of knowledge is empirical; knowledge comes to us from the world through ‘appearances’, which are impressed on our minds. Reason, seen as the quintessentially human characteristic, enables us to understand the world. Stoicism denied the importance of all bodily conditions, and emotions were always regarded as bad. The only factor seen as essential to human happiness was virtue, all else in life having significance only as an opportunity to demonstrate that one possesses virtue. Seneca claimed that one could demonstrate virtue equally well through pleasure or through pain, whether enjoying a banquet or submitting to torture. For the Stoic, poverty and detachment from the world were not seen as essential for the achievement of the good life, nor need worldly wealth be abandoned in the quest for virtue.
In the treatise De Officiis (On Duties), written after the assassination of Julius Caesar in 44 BC, the Roman politician and philosopher Cicero gave a Stoic account of the correct use of the body as part of his advice to his son — and to the Roman governing classes in general — on how to make moral decisions and to live in the best way possible. As a manual for the upper classes, this text was highly influential in Western political and social thought. Cicero says that both the mind and the body should be trained from childhood into moderate and appropriate behavior, and this should be expressed through every action — there being a seemly way to stand, walk, or sit. The ideal is to control the body, avoid excessive gestures, and follow a moderate way of life. Stoics believe that humans should confront life calmly. The basis of Stoic philosophy was an ethic of the consolations of identification with the impartial, inevitable, moral order of the universe. It is an ethic of self-sufficient, benevolent calm, with the virtuous peace of the wise man rendering him indifferent to poverty, pain, and death, so resembling the spiritual peace of God.