Stoicism, a school of philosophy, was founded in Athens in the early third century. It concerns the active relationship between cosmic determinism and human freedom, and the belief that it is virtuous to maintain a will that is in accord with nature. The Stoics presented their philosophy as a way of life, and they thought that the best indication of an individual’s philosophy was not what a person said but how they behaved.
According to the Stoics, the senses are constantly receiving sensations as pulsations which pass from objects through the senses to the mind, where they leave behind an impression. The mind has the ability to approve or reject an impression, to enable it to distinguish a representation of reality which is true from one which is false. Some impressions can be assented to immediately, but others can only achieve varying degrees of approval which can be labelled belief or opinion.
Stoics believe in the universe as a material reasoning, substance known as God or Nature, which they divided into two classes, the active and the passive. The passive substance is matter, which was interpreted as a substance ready for any use, but sure to remain unemployed if no one set it in motion.
The active substance, which could be called Fate, is an intelligent aether or primordial fire, which acts on the passive matter. The universe itself is God and the universal outpouring of its soul. It is this world’s guiding principle, operating in mind and reason, together with the common nature of things and the totality which embraces all existence.
Everything is subject to the laws of Fate, for the Universe acts only according to its own nature, and the nature of the passive matter which it governs. The souls of people and animals are emanations from this primordial fire, and are likewise subject to Fate.
A distinctive feature of Stoicism is its cosmopolitanism. All people are manifestations of the one universal spirit and should, according to the Stoics, live in brotherly love and readily help one another. Each human being is primarily a citizen of his own commonwealth, but is also a member of the great city of gods and men, where of the political city is only a copy. This sentiment echoes that of Socrates, who said “I am not an Athenian or a Greek, but a citizen of the world.”
They held that external differences such as rank and wealth are of no importance in social relationships. Thus, before the rise of Christianity, Stoics advocated the brotherhood of humanity and the natural equality of all human beings. Stoicism became the most influential school of the Greco–Roman world, and produced a number of remarkable writers and personalities.
The Stoics provided a unified account of the world, consisting of formal logic, non dualistic physics and naturalistic ethics. Of these, they emphasized ethics as the main focus of human knowledge, though their logical theories were to be of more interest for many later philosophers.
Stoicism teaches the development of self-control and fortitude as a means of overcoming destructive emotions. The philosophy holds that becoming a clear and unbiased thinker allows one to understand the universe. A primary aspect of Stoicism involves improving the individual’s ethical and moral well-being.
The Stoics believed in the certainty of knowledge, which can be attained through the use of reason. Truth can be distinguished from fallacy, even if in practice only an approximation can be made.