To render a federation advisable several conditions are necessary. The first is that there should be a sufficient amount of mutual sympathy among the populations. The federation binds them always to fight on the same side; and if they have such feelings toward one another, or such diversity of feeling toward their neighbors that they would generally prefer to fight on opposite sides, the federal tie is neither likely to be of long duration, nor to be well observed while it subsists. The sympathies available for the purpose are those of race, language, religion, and, above all, of political institutions, as conducing most to a feeling of identity of political interest. When a few free states, separately insufficient for their own defense, are hemmed in on all sides by military or feudal monarchs, who hate and despise freedom even in a neighbor, those states have no chance for preserving liberty and its blessings but by a federal union. The common interest arising from this cause has in Switzerland, for several centuries, been found adequate to maintain efficiently the federal bond, in spite not only of difference of religion when religion was the grand source of irreconcilable political enmity throughout Europe, but also in spite of great weakness in the constitution of the federation itself. In America, where all the conditions for the maintenance of union existed at the highest point, with the sole drawback of difference of institutions in the single but most important article of slavery, this one difference goes so far in alienating from each other's sympathies the two divisions of the Union as to be now actually effecting the disruption of a tie of so much value to them both. A second condition of the stability of a federal government is that the separate states be not so powerful as to be able to rely for protection against foreign encroachment on their individual strength. If they are, they will be apt to think that they do not gain, by union with others, the equivalent of what they sacrifice in their own liberty of action; and consequently, whenever the policy of the confederation, in things reserved to its cognizance, is different from that which any one of its members would separately pursue, the internal and sectional breach will, through absence of sufficient anxiety to preserve the Union, be in danger of going so far as to dissolve it.