Jean-Jacques Rousseau

Jean-Jacques Rousseau was a French Enlightenment philosopher and writer born in Geneva, Switzerland. He believed that the natural goodness of man was warped by society, and his ideas warped the French Revolution. He managed to get both the French and the Swiss pissed at him, so that's something.

Philosophy
Rousseau's core philosophy has a tendency to get either misrepresented or outright strawmanned, depending on who's doing the criticizing. His work was largely a response to Thomas Hobbes (1588-1679), who argued that pre-society humans were violent and brutal to one another. Rousseau, however, posited that pre-society humans were largely docile, timid, and solitary - furthermore, they were completely amoral, as morality and concepts of justice could, in his view, only be established through a social contract. Rousseau believed that active hatred of one's fellow man - and other corrupting values - had to be learned through society, which he argued - by yelling at clouds through his writing - was happening during his time. Hence he advocated for developmental education in children, aimed at combating this and increasing our autonomy, which he thought was the best way to preserve our typical docile roots.

This ends up being flanderized into the belief that Rousseau saw all humans as inherently good - an interpretation of Rousseau shared even by some of his contemporaries, such as Voltaire (1694-1778). In reality, Rousseau thought humans were "good" in so far as pre-society peoples didn't actively bite each other's throats out but mostly kept to themselves, which isn't quite the same thing.

Rousseau also believed that personal freedom and authoritative power would need to be in balance in an effective society, this balance would be kept by the concept of a general will, the collective will of the citizen body, as the source of law in a state.

Since both Rousseau's and Hobbes' conception of a "State of Nature" predate Darwin's research, and since our common ancestors are now widely known to have been social animals, it seems unlikely that human beings ever existed without some form of a society present. As such, saying that society corrupted us or is the only thing keeping us from burning our neighbors' house down might be a tad simplistic in light of new information.