Diogenes of Sinope (Greek: Διογένης ὁ Σινωπεύς Diogenes ho Sinopeus), was a Greek philosopher and one of the founders of Cynic philosophy. Also known as Diogenes the Cynic, he was born in Sinope (modern-day Sinop, Turkey) in 412 or 404 BCE and died at Corinth in 323 BCE.
Diogenes was one of the few men to ever publicly mock Alexander the Great and live. He intellectually humiliated Plato and was the only pupil ever accepted by Antisthenes, whom he saw as the true heir of Socrates. Diogenes taught his philosophy of Cynicism to Crates who taught it to Zeno of Citium who fashioned it into the school of Stoicism, one of the most enduring branches of Greek philosophy.
— Alexander and Diogenes, Caspar de Crayer (1582-1669)
When Plato styled him a dog, Diogenes said:
Quite true, for I come back again and again to those who have sold me.
— Diogenes, Jean-Léon Gérôme (1824-1904)