Language is a dangerous thing in revolutionary times since it implies old, wild, non rational thought which does not fit into the brave new world of rationally enlightened political affairs. How to make our (linguistically obscure) ideas clear is the philosophical and political problem of the Revolution. The paper sketches the development of the revolutionary language theory from Bacon via Locke and Condillac. And it shows how the French Revolution fights against that wild thought in language by a politics of annihilation of the regional languages and of purification of the French language itself. Even if France today is trying to find a way back to a politics of linguistic diversity, the global revolution of languages is more likely to win.