Diogenes was a noted Greek philosopher who became famous as the father of Cynicism. As a cynic, Diogenes rejected human norms and conventions, attempting to live a life as close to nature as possible in order to free his mind. No known writings of Diogenes survive; what we know about him comes from writings by followers and contemporaries, who described some of his exploits at great length. In some cases, it is difficult to tell where the mark between legend and reality falls with Diogenes, because a huge body of mythology arose around the man and his peculiar life.
He was born around 400 BCE in Sinope, and all evidence suggests that he was either exiled or encouraged to leave as a young man as a punishment for defacing currency. From Sinope, he made his way to Athens, ultimately ending up in Corinth and dying around 325 BCE. Along the way, Diogenes attracted a great deal of attention with his radical views, famously shedding all of his worldly possessions one by one.
According to Diogenes, one's mind had to be free in order to seek wisdom, and this meant that it was necessary to ignore things like wealth, rank, privilege, and other human conventions. In addition, he advocated a more frank, natural lifestyle, famously using dogs as an inspiration. Diogenes pointed out that dogs are comfortable doing just about anything in public, and he followed suit, famously defecating in public squares, urinating on people he didn't like, and indulging in a variety of lewd acts in plain view.
”Cynic” in fact comes from the Ancient Greek word for dog, kyon, and Diogenes advocated a doglike life of simplicity and frank honesty. He had few possessions, living a life of poverty in the streets; he is said to have broken his last possession, a bowl, upon seeing a peasant drink out of his hands. In Athens, Diogenes greatly enjoyed antagonizing other philosophers, and he wandered the city with a lit lamp during the daytime, saying that he was looking for an honest man.
By all accounts, Diogenes had a very sharp tongue, and an acerbic wit. In his eyes, nothing was sacred, and everything provided an opportunity for mockery and deconstruction, given time. For example, upon hearing Plato's statement that man is a featherless biped with two legs, Diogenes triumphantly presented Plato with a plucked chicken.