Political philosophers frequently find that half their task is defining the very words they use, for how one demarcates terms will affect how one thinks through political problems. Indeed, we can see this throughout the entire history of Western political thought. In attempting to explain this basic term, he concluded that justice was to be found in a society with a proper division of labor, in which everybody plays the role for which he or she is naturally best suited. Plato and Rawls obviously reached different conclusions when trying to define justice. The impact has been more than you might imagine.
Ideas are, of course, only one element of what makes history.
Still, how people think politically very much affects how they act politically. Rousseau wrote that we are politically free when we are subject to laws we have formulated ourselves. These were subversive ideas in prerevolutionary France, a hierarchical society in which the Crown was sovereign and the inhabitants of this realm were the King's subjects, not self-governing citizens. Its author had to flee into exile. For another example, take a case closer to home.