Jean-Jacques Rousseau was a Genevan philosopher whose ideas were among the most radical of the Enlightenment.

He famously argued that humans are naturally good but are corrupted by society, a view that contrasted with many of his contemporaries.

His most important political work, 'The Social Contract,' begins with the famous line, 'Man is born free, and everywhere he is in chains.'

Rousseau proposed that a legitimate government must be based on the 'general will,' the collective will of the entire citizen body.

This concept of popular sovereignty holds that ultimate political authority rests with the people.

He believed in a direct democracy where citizens participate actively in making laws.

His work 'Emile, or On Education' outlined his ideas on education, emphasizing learning through experience and discovery.

Rousseau's emphasis on emotion and nature also made him a key forerunner of the Romantic movement.

His ideas were highly influential on the more radical Jacobin phase of the French Revolution.

Rousseau's political philosophy remains both celebrated for its democratic ideals and controversial for its potential to be interpreted in a totalitarian way.