From A Discourse in Political Economy by Jean-Jacques Rousseau (1755):
The first and most important rule of legitimate or popular government, that is to say, of government whose object is the good of the people, is therefore, as I have observed, to follow in everything the general will. But to follow this will it is necessary to know it, and above all to distinguish it from the particular will, beginning with one's self: this distinction is always very difficult to make, and only the most sublime virtue can afford sufficient illumination for it. As, in order to will, it is necessary to be free, a difficulty no less great than the former arises ? that of preserving at once the public liberty and the authority of government.
Could you possibly explain the words in bold? I have read it 10 times in total, but I still don't understand it yet. And, should that the question mark be there?