Almost every great epoch in history has been devoted to some question, if not an exclusive one, at least one dominant both in events and opinions, and around which the varying opinions and the efforts of men were concentrated. Not to go farther back than the era of modern history--in the sixteenth century the question of the unity of Religion and of its Reform; in the seventeenth century the question of pure monarchy, with its conquests abroad and administration at home; in the eighteenth century that of the operation of civil and religious liberty: such have been in France the different points on which ideas have culminated, the different objects which each social movement had specially in view. {xii} The systems of the day, although opposed, were clear; the struggles ardent but well defined. Men walked in those days on high roads; they did not wander about in the infinite complications of a labyrinth. And it is in a very labyrinth of questions and of ideas, of essays and events, diverse in character, confused, incoherent, contradictory, in which in these days the civilized world is plunged. I do not pretend to seize the clue to the labyrinth; I propose but to throw some light upon the chaos. First I turn my eyes to the external situation and relations of the States of Christendom, and consider the questions which concern the boundaries of territories and the distribution of populations between distinct and independent nations. Formerly these questions were all reducible to one--the aggrandizement or the weakening of these different States, and the maintenance or the disturbance of that balance of forces which was called the balance of power in Europe. {xiii} War and Diplomacy, Conquests and Treaties, discussed and settled this supreme question, of which Grotius expounded the theory, and Ancillon wrote the history. Now we are no longer in a situation so simple. What a complication of ideas: what ideas, novel and ill-defined, start up in these days to embarrass the course and entangle the relations of States! The question of races, the question of nationalities, the question of little states and of great political unities, the question of popular sovereignty and of its rights beyond the limits of nations as well as in their midst,--all these problems arise and cast into the shade, as a routine which has served its turn, the old public right and the maxims of the equilibrium of Europe, in their place seeking themselves to impose rules for regulating the territorial organizations and the external relations of States. {xiv}