To solve the first problem—that, namely, of political expediency—much knowledge of nature is required, that her mechanical laws may be employed for the end in view. And yet the result of all knowledge of this kind is uncertain, as far as perpetual peace is concerned. This we find to be so, whichever of the three departments of public law we take. It is uncertain whether a people could be better kept in obedience and at the same time prosperity by severity or by baits held out to their vanity; whether they would be better governed under the sovereignty of a single individual or by the authority of several acting together; whether the combined authority might be better secured merely, say, by an official nobility or by the power of the people within the state; and, finally, whether such conditions could be long maintained. There are examples to the contrary in history in the case of all forms of government, with the exception of the only true republican constitution, the idea of which can occur only to a moral politician. Still more uncertain is a law of nations, ostensibly established upon statutes devised by ministers; for this amounts in fact to mere empty words, and rests on treaties which, in the very act of ratification, contain a secret reservation of the right to violate them. On the other hand, the solution of the second problem—the problem of political wisdom—forces itself, we may say, upon us; it is quite obvious to every one, and puts all crooked dealings to shame; it leads, too, straight to the desired end, while at the same time, discretion warns us not to drag in the conditions of perpetual peace by force, but to take time and approach this ideal gradually as favourable circumstances permit.