This scheme of a federation of the nations of the world, in accordance with principles which would put an end to war between them, was one whose interest for Kant seemed to increase during the last twenty years of his life.[60] It was according to him an idea of reason, and, in his first essay on the subject—that of 1784—we see the place this ideal of a perpetual peace held in the Kantian system of philosophy. Its realisation is the realisation of the highest good—the ethical and political _summum bonum_, for here the aims of morals and politics coincide: only in a perfect development of his faculties in culture and in morals can man at last find true happiness. History is working towards the consummation of this end. A moral obligation lies on man to strive to establish conditions which bring its realisation nearer. It is the duty of statesmen to form a federative union as it was formerly the duty of individuals to enter the state. The moral law points the way here as clearly as in the sphere of pure ethics:—“Thou can’st, therefore thou ought’st.” [60] The immediate stimulus to Kant’s active interest in this subject as a practical question was the Peace of Basle (1795) which ended the first stage in the series of wars which followed the French Revolution. Let us be under no misapprehension as to Kant’s attitude to the problem of perpetual peace. It is an ideal. He states plainly that he so regards it[61] and that as such it is unattainable. But this is the essence of all ideals: they have not the less value in shaping the life and character of men and nations on that account. They are not ends to be realised but ideas according to which we must live, regulative principles. We cannot, says Kant, shape our life better than in acting as if such ideas of reason have objective validity and there be an immortal life in which man shall live according to the laws of reason, in peace with his neighbour and in freedom from the trammels of sense. [61] It is _eine unausführbare Idee_. See the passage quoted from the _Rechtslehre_, p. 129, _note_. Hence we are concerned here, not with an end, but with the means by which we might best set about attaining it, if it were attainable. This is the subject matter of the _Treatise on Perpetual Peace_ (1795), a less eloquent and less purely philosophical essay than that of 1784, but throughout more systematic and practical. We have to do, not with the favourite dream of philanthropists like St. Pierre and Rousseau, but with a statement of the conditions on the fulfilment of which the transition to a reign of peace and law depends. _The Conditions of the Realisation of the Kantian Ideal._