Cynicism is a school of philosophy from the Socratic period of ancient Greece, which holds that the purpose of life is to live a life of Virtue in agreement with Nature (which calls for only the bare necessities required for existence). This means rejecting all conventional desires for health, wealth, power and fame, and living a life free from all possessions and property.
Cynics lived in the full glare of the public's gaze and aimed to be quite indifferent in the face of any insults which might result from their unconventional behavior. They saw part of their job as acting as the watchdog of humanity, and to evangelize and hound people about the error of their ways, particularly criticizing any show of greed, which they viewed as a major cause of suffering. Many of their ideas (see the section on the doctrine of Cynicism for more details) were later absorbed into Stoicism.
The founder of Cynicism as a philosophical movement is usually considered to be Antisthenes (c. 445 - 365 B.C.), who had been one of the most important pupils of Socrates in the early 5th Century B.C. He preached a life of poverty, but his teachings also covered language, dialogue and literature in addition to the pure Ethics which the later Cynics focused on.
Antisthenes was followed by Diogenes of Sinope, who lived in a tub on the streets of Athens, and ate raw meat, taking Cynicism to its logical extremes. Diogenes dominates the story of Cynicism like no other figure, and he came to be seen as the archetypal Cynic philosopher. He dedicated his life to self-sufficiency ("autarkeia"), austerity ("askesis") and shamelessness ("anaideia"), and was famed for his biting satire and wit.
Crates of Thebes (c. 365 - 285 B.C.), who gave away a large fortune so he could live a life of poverty in Athens, was another influential and respected Cynic of the period. Other notable Greek Cynics include Onesicritus (c. 360 - 290 B.C.), Hipparchia (c. 325 B.C.), Metrocles (c. 325 B.C.), Bion of Borysthenes (c. 325 - 255 B.C.), Menippus (c. 275 B.C.), Cercidas (c. 250 B.C.) and Teles (c. 235 B.C.).
With the rise of Stoicism in the 3rd Century B.C., Cynicism as a serious philosophical activity underwent a decline, and it was not until the Roman era that there was a Cynic revival. Cynicism spread with the rise of Imperial Rome in the 1st Century A.D., and Cynics could be found begging and preaching throughout the cities of the Roman Empire, where they were treated with a mixture of scorn and respect. Cynicism seems to have thrived into the 4th Century A.D., unlike Stoicism, which had long declined by that time. Notable Roman Cynics include Demetrius (c. 10 - 80 A.D.), Demonax (c. 70 - 170 A.D.), Oenomaus (c. 120 A.D.), Peregrinus Proteus (c. 95 - 167 A.D.) and Sallustius (c. 430 - 500 A.D.).
Cynicism finally disappeared in the late 5th Century A.D., although many of its ascetic ideas and rhetorical methods were adopted by early Christians.