4th Century BC : Along with Antisthenes and Crates of Thebes, Diogenes is considered one of the founders of Cynicism. The ideas of Diogenes, like those of most other Cynics, must be arrived at indirectly. No writings of Diogenes survived even though he is reported to have authored over ten books, a volume of letters and seven tragedies. Cynic ideas are inseparable from Cynic practice; therefore what we know about Diogenes is contained in anecdotes concerning his life and sayings attributed to him in a number of scattered classical sources. Diogenes maintained that all the artificial growths of society were incompatible with happiness and that morality implies a return to the simplicity of nature. So great was his austerity and simplicity that the Stoics would later claim him to be a wise man or “sophos”. Diogenes had nothing but disdain for Plato and his abstract philosophy. Diogenes viewed Antisthenes as the true heir to Socrates, and shared his love of virtue and indifference to wealth, together with a disdain for general opinion. Diogenes shared Socrates' belief that he could function as doctor to men's souls and improve them morally, while at the same time holding contempt for their obtuseness. Plato once described Diogenes as “a Socrates gone mad.” Many anecdotes of Diogenes refer to his dog-like behavior, and his praise of a dog's virtues.