Diogenes "the Cynic" was an ancient Greek philosopher born in Sinope, an Ionian colony on the Black Sea, probably in 412 BC. He was exiled either because he counterfeited the local currency or he had followed his father who was accused of counterfeiter. Diogenes moved to Athens in 370 BC and was impressed by the teaching of Antisthenes, founder of the school of cynical philosophers, one of the most eminent disciples of Socrates. He tried to become a disciple of Antisthenes who preached publicly that there should be no government, courts, private property, official religion, marriage, but Antisthenes refused to teach a former banker. Diogenes insisted for a long time until Antisthenes decided to admit him when he saw him dressed in rags and sleeping outside on dirt.
Diogenes very soon surpassed his teacher, not only in reputation but also in the strictness of his lifestyle. Many attribute to him the introduction of cynical lifestyle. The cynical philosophy called so because the cynics have as their emblem a Cyon (dog) and said "we differ from other dogs because we don’t bite our enemies, we bite our friends only to correct them". Cynics philosophers professed ultimate questioning of everything, rejected all authority and wanted the absolute freedom of people.
Diogenes believed that humans are naturally equipped with everything they need and have no need for unnecessary things. They manufacture numerous artificial needs and desires that eventually enslave them. Only the satisfaction of physical needs leads to happiness and no such need should be considered immoral, since nature has created all. However the physical needs should be minimized, so people will easily meet them and be self-sufficient. He rejected the polytheism and religion as arbitrary human institutions. He laughed at Orators who made much noise about justice but never applied it in their lives. He said that people are struggling to outdo one another in material possessions, but nobody is fighting to become a better person. Practicing his beliefs, he circulated in Athens barefoot, wearing always the same clothe, only in severe winter he was borrowing a cloak. He slept without bedding in a tub, accompanied by his dogs. He never created a family and considered himself a citizen of the world. He used the cynicism and the pun as a means for his teachings.
In a trip to Aegina Diogenes was captured by pirates and sold as a slave in Crete. Impressed by his spirit, Xeniades bought him and took him to Corinth. There he entrusted him with the upbringing of his two sons. Diogenes lived the rest of his life in Corinth, preaching the cynical philosophy, until his death in 323 BC.