Painting: Diogenes the Cynic telling Alexander the Great to stop blocking the sunshine.
An excerpt from, "Greek Philosopher: Diogenes":
According to a popular story, on one occasion Diogenes had an interview with Alexander III, King of Macedonia. The king opened the conversation with "I am Alexander the Great", and the philosopher answered, "And I am Diogenes the Cynic".Wikipedia:
Alexander then asked him in what way he could serve him. "You can stand out of the sunshine," the philosopher replied. Alexander is said to have been so struck with the Cynic's self-possession that he went away remarking, "If I were not Alexander, I would wish to be Diogenes."
Diogenes died at Corinth, according to tradition, on the same day as Alexander.
Diogenes of Sinope was a Greek philosopher and one of the founders of Cynic philosophy. Also known as Diogenes the Cynic (Ancient Greek: Διογένης ὁ Κυνικός, Diogenēs ho Kunikos), he was born in Sinope (modern-day Sinop, Turkey), an Ionian colony on the Black Sea, in 412 or 404 BC and died at Corinth in 323 BC.YouTube video description [Channel - Gottfried Leibniz]:
Diogenes of Sinope was a controversial figure. His father minted coins for a living and when Diogenes took to "defacement of the currency", he was banished from the city. After being exiled, he moved to Athens to debunk cultural conventions. Diogenes modelled himself on the example of Hercules. He believed that virtue was better revealed in action than in theory. He used his simple lifestyle and behaviour to criticise the social values and institutions of what he saw as a corrupt society. He declared himself a cosmopolitan. There are many tales about him dogging Antisthenes' footsteps and becoming his faithful hound, but it is by no means certain that the two men ever met. Diogenes made a virtue of poverty. He begged for a living and slept in a jar in the marketplace. He became notorious for his philosophical stunts such as carrying a lamp in the daytime, claiming to be looking for an honest man. He embarrassed Plato, disputed his interpretation of Socrates and sabotaged his lectures. Diogenes was also responsible for publicly mocking Alexander the Great.
After being captured by pirates and sold into slavery, Diogenes eventually settled in Corinth. There he passed 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 schools of Greek philosophy. None of Diogenes’ many writings has survived, but details of his life come in the form of anecdotes (chreia), especially from Diogenes Laërtius, in his book Lives and Opinions of Eminent Philosophers. All we have is a number of anecdotes concerning his life and sayings attributed to him in a number of scattered classical sources, none of them definitive.
Peter Adamson discusses the history of cynicism.