One of the biggest, most revolutionary ideas within the Declaration of the Rights of Man and Citizen is popular sovereignty. You know: letting the people participate in their government by voting politicians in and out of office.

One of the Enlightened philosophers who suggested popular sovereignty was the Englishman John Locke. He wasn't the first to come up with it, but through his writings he repeatedly championed the idea that people should be allowed some kind of say in their government.

Like most Enlightenment thinkers, he was stealing ideas from the republic of ancient Rome and updating them with modern ideas of representation that reflected the will of the people. His thoughts would probably not have been popular with King Louis XVI, who thought that the only government participation people should have is politely asking him for something.