Rousseau and the need for Virtue
If Voltaire was the prime example of an Enlightenment philosophe who promoted reason as the essential characteristic of human beings, the other tradition of Enlightenment thought which emphasized virtue was embodied by Jean-Jacques Rousseau.
Rousseau was born in the city of Geneva, which meant he was a Calvinist and a citizen of a republic. He was, like Diderot, the son of a watchmaker, who educated Jean-Jacques informally but intensely. As a teenager, the young Rousseau left for Paris, converting to Catholicism along the way. He was very interested in the Enlightenment, but concerned that its emphasis on reason as the source of all useful knowledge was misguided.
In 1750 he became well known for an essay in which he argued that despite what the philosophes said practical knowledge did not contributed to morality at all; instead it had corrupted people's morals in Europe, because it had encouraged people to become reliant on others rather than producing all they need for themselves. He considered such a situation to be unnatural, because it inevitably led to inequality (moral, political and economic) among people.