When the conditions exist for the formation of efficient and durable federal unions, the multiplication of them is always a benefit to the world. It has the same salutary effect as any other extension of the practice of co-operation, through which the weak, by uniting, can meet on equal terms with the strong. By diminishing the number of those petty states which are not equal to their own defense, it weakens the temptations to an aggressive policy, whether working directly by arms, or through the _prestige_ of superior power. It of course puts an end to war and diplomatic quarrels, and usually also to restrictions on commerce, between the states composing the Union; while, in reference to neighboring nations, the increased military strength conferred by it is of a kind to be almost exclusively available for defensive, scarcely at all for aggressive purposes. A federal government has not a sufficiently concentrated authority to conduct with much efficiency any war but one of self-defense, in which it can rely on the voluntary co-operation of every citizen; nor is there any thing very flattering to national vanity or ambition in acquiring, by a successful war, not subjects, nor even fellow-citizens, but only new, and perhaps troublesome independent members of the confederation. The warlike proceedings of the Americans in Mexico was purely exceptional, having been carried on principally by volunteers, under the influence of the migratory propensity which prompts individual Americans to possess themselves of unoccupied land, and stimulated, if by any public motive, not by that of national aggrandizement, but by the purely sectional purpose of extending slavery. There are few signs in the proceedings of Americans, nationally or individually, that the desire of territorial acquisition for their country as such has any considerable power over them. Their hankering after Cuba is, in the same manner, merely sectional, and the Northern States, those opposed to slavery, have never in any way favored it.