Diogenes of Sinope (c.412-c.323): Greek sculptor, co-founder of the Cynical school.
Diogenes of Sinope was a student of Antisthenes. Both men are called the founder of the school that is known as Cynicism. The essential point in this world-view is that man suffers from too much civilization. We are happiest when our life is simplest, which means that we have to live in accordance with nature - just like animals.
Human culture, however, is dominated by things that prevent simplicity: money, for example, and our longing for status. Like his master, Diogenes refrained from luxury and often ridiculed civilized life.
His philosophy gained some popularity because he focused upon personal integrity, whereas men like Plato and Aristotle of Stagira had been thinking about man's life and honor as member of a city state - a type of political unit that was losing importance in the age of Alexander the Great (who once met Diogenes; text).
However, we can not return to nature. The Cynics became a kind of jesters, accepted at the royal courts because their criticism was essentially harmless.
A biography was included in the Lives of Eminent Philosophers by Diogenes Laertius (here).