aggressive war if it were fairly certain in advance that the aggressor must be defeated. This could be achieved if most great nations came to regard the peace of the world as of such importance that they would side against an aggressor even in a quarrel in which they had no direct interest. It is on this hope that the League of Nations is based.
But the League of Nations, like the abolition of private property, will be by no means sufficient if it is not accompanied or quickly followed by other reforms. It is clear that such reforms, if they are to be effective, must be international; the world must move as a whole in these matters, if it is to move at all. One of the most obvious necessities, if peace is to be secure, is a measure of disarmament. So long as the present vast armies and navies exist, no system can prevent the risk of war. But disarmament, if it is to serve its purpose, must be simultaneous and by mutual agreement among all the Great Powers. And it is not likely to be successful so long as hatred and suspicion rule between nations, for each nation will suspect its neighbour of not carrying out the bargain fairly. A different mental and moral atmosphere from that to which we are accustomed in international affairs will be necessary if agreements between nations are to succeed in averting catastrophes. If once such an atmosphere existed, it might be perpetuated by wise institutions; but it cannot be created by institutions alone. International co-operation requires mutual goodwill, and goodwill, however it has arisen, is only to be preserved by co-operation. The international
