According to one story, Diogenes went to the Oracle at Delphi to ask for her advice and was told that he should "deface the currency".
Following the debacle in Sinope, Diogenes decided that the oracle meant that he should deface the political currency rather than actual coins.
He traveled to Athens and made it his life's goal to challenge established customs and values.
He argued that instead of being troubled about the true nature of evil, people merely rely on customary interpretations.
This distinction between nature ("physis") and custom ("nomos") is a favourite theme of ancient Greek philosophy, and one that Plato takes up in The Republic, in the legend of the Ring of Gyges.

Diogenes arrived in Athens with a slave named Manes who escaped from him shortly thereafter.
With characteristic humor, Diogenes dismissed his ill fortune by saying, "If Manes can live without Diogenes, why not Diogenes without Manes?"
 Diogenes would mock such a relation of extreme dependency.
He found the figure of a master who could do nothing for himself contemptibly helpless.
He was attracted by the ascetic teaching of Antisthenes, a student of Socrates.
When Diogenes asked Antisthenes to mentor him, Antisthenes ignored him and reportedly "eventually beat him off with his staff".
Diogenes responds, "Strike, for you will find no wood hard enough to keep me away from you, so long as I think you've something to say."
Diogenes became Antisthenes' pupil, despite the brutality with which he was initially received.
 Whether the two ever really met is still uncertain, but he surpassed his master in both reputation and the austerity of his life.
He considered his avoidance of earthly pleasures a contrast to and commentary on contemporary Athenian behaviors.
This attitude was grounded in a disdain for what he regarded as the folly, pretence, vanity, self-deception, and artificiality of human conduct.

The stories told of Diogenes illustrate the logical consistency of his character.
He inured himself to the weather by living in a clay wine jar belonging to the temple of Cybele.
He destroyed the single wooden bowl he possessed on seeing a peasant boy drink from the hollow of his hands.
He then exclaimed: "Fool that I am, to have been carrying superfluous baggage all this time!"
It was contrary to Athenian customs to eat within the marketplace, and still he would eat there, for, as he explained when rebuked, it was during the time he was in the marketplace that he felt hungry.
He used to stroll about in full daylight with a lamp; when asked what he was doing, he would answer, "I am just looking for an honest man."
Diogenes looked for a human being but reputedly found nothing but rascals and scoundrels.

According to Diogenes Laërtius, when Plato gave the tongue-in-cheek definition of man as "featherless bipeds," Diogenes plucked a chicken and brought it into Plato's Academy, saying, "Behold!
I've brought you a man," and so the Academy added "with broad flat nails" to the definition.
According to one story, Diogenes went to the Oracle at Delphi to ask for her advice and was told that he should "deface the currency". Following the debacle in Sinope, Diogenes decided that the oracle meant that he should deface the political currency rather than actual coins. He traveled to Athens and made it his life's goal to challenge established customs and values. He argued that instead of being troubled about the true nature of evil, people merely rely on customary interpretations. This distinction between nature ("physis") and custom ("nomos") is a favourite theme of ancient Greek philosophy, and one that Plato takes up in The Republic, in the legend of the Ring of Gyges.
Diogenes arrived in Athens with a slave named Manes who escaped from him shortly thereafter. With characteristic humor, Diogenes dismissed his ill fortune by saying, "If Manes can live without Diogenes, why not Diogenes without Manes?"  Diogenes would mock such a relation of extreme dependency. He found the figure of a master who could do nothing for himself contemptibly helpless. He was attracted by the ascetic teaching of Antisthenes, a student of Socrates. When Diogenes asked Antisthenes to mentor him, Antisthenes ignored him and reportedly "eventually beat him off with his staff". Diogenes responds, "Strike, for you will find no wood hard enough to keep me away from you, so long as I think you've something to say." Diogenes became Antisthenes' pupil, despite the brutality with which he was initially received.  Whether the two ever really met is still uncertain, but he surpassed his master in both reputation and the austerity of his life. He considered his avoidance of earthly pleasures a contrast to and commentary on contemporary Athenian behaviors. This attitude was grounded in a disdain for what he regarded as the folly, pretence, vanity, self-deception, and artificiality of human conduct.
The stories told of Diogenes illustrate the logical consistency of his character. He inured himself to the weather by living in a clay wine jar belonging to the temple of Cybele. He destroyed the single wooden bowl he possessed on seeing a peasant boy drink from the hollow of his hands. He then exclaimed: "Fool that I am, to have been carrying superfluous baggage all this time!" It was contrary to Athenian customs to eat within the marketplace, and still he would eat there, for, as he explained when rebuked, it was during the time he was in the marketplace that he felt hungry. He used to stroll about in full daylight with a lamp; when asked what he was doing, he would answer, "I am just looking for an honest man." Diogenes looked for a human being but reputedly found nothing but rascals and scoundrels.
According to Diogenes Laërtius, when Plato gave the tongue-in-cheek definition of man as "featherless bipeds," Diogenes plucked a chicken and brought it into Plato's Academy, saying, "Behold! I've brought you a man," and so the Academy added "with broad flat nails" to the definition.
Diogenes