Diogenes was always controversial. Exiled from his native city for defacing the currency, he moved to Athens and declared himself a cosmopolitan (in defiance of the prevailing city-state system). He became a disciple of Antisthenes, and made a virtue of extreme poverty, famously begging for a living and sleeping in a tub in the marketplace.

He became notorious for his provocative behaviour and philosophical stunts such as carrying a lamp in the daytime, claiming to be looking for an honest man. He regularly argued with Plato, disputing his interpretation of Socrates and sabotaging his lectures. After being captured by pirates and sold into slavery, Diogenes eventually settled in Corinth, where he was admired by Alexander.