Vom Geist der Gesetze
French philosophers produced some of the most important political works of the Age of Enlightenment. In "The Spirit of the Laws", Baron de Montesquieu theorised the principle of separation of powers, which has been implemented in all liberal democracies since it was first applied in the United States. Voltaire came to embody the Enlightenment with his defence of civil liberties, such as the right to a free trial and freedom of religion.