Diogenes of Sinope was a Greek philosopher and one of the founders of Cynic philosophy. Also known as Diogenes the Cynic, he was born in Sinope, an Ionian colony on the Black Sea, in 412 or 404 BCE and died at Corinth in 323 BCE.

Diogenes of Sinope was a controversial figure. His father minted coins for a living, and when Diogenes took to debasement of currency, he was banished from Sinope. After being exiled, he moved to Athens and criticized many cultural conventions of the city. Diogenes modelled himself on the example of Heracles. He believed that virtue was better revealed in action than in theory. He used his simple lifestyle and behaviour (which arguably resembled poverty) to criticize the social values and institutions of what he saw as a corrupt or at least confused society. In a highly non-traditional fashion, he had a reputation of sleeping and eating wherever he chose and took to toughening himself against nature. He declared himself a cosmopolitan and a citizen of the world rather than claiming allegiance to just one place. There are many tales about him dogging Antisthenes' footsteps and becoming his "faithful hound". Diogenes made a virtue of poverty. He begged for a living and often slept in a large ceramic jar in the marketplace. He became notorious for his philosophical stunts such as carrying a lamp in the daytime, claiming to be looking for an honest man. He criticized and embarrassed Plato, disputed his interpretation of Socrates and sabotaged his lectures, sometimes distracting attendees by bringing food and eating during the discussions. Diogenes was also noted for having publicly mocked Alexander the Great.

Diogenes taught by living example. He tried to demonstrate that wisdom and happiness belong to the man who is independent of society and that civilization is regressive. He scorned not only family and political social organization, but also property rights and reputation. He even rejected normal ideas about human decency. Diogenes is said to have eaten in the marketplace, urinated on some people who insulted him, defecated in the theatre, and masturbated in public. When asked about his eating in public he said, "If taking breakfast is nothing out of place, then it is nothing out of place in the marketplace. But taking breakfast is nothing out of place, therefore it is nothing out of place to take breakfast in the marketplace." On the indecency of him masturbating in public he would say, "If only it were as easy to banish hunger by rubbing my belly."

From Life of Diogenes: "Someone took him [Diogenes] into a magnificent house and warned him not to spit, whereupon, having cleared his throat, he spat into the man's face, being unable, he said, to find a meaner receptacle."

https://en.wikipedia.org/wiki/Diogenes_of_Sinope