War arises because of the changing relations of numerous variables--technological, psychic, social, and intellectual. There is no single cause of war. Peace is an equilibrium among many forces. Change in any particular force, trend, movement, or policy may at one time make for war, but under other conditions a similar change may make for peace. A state may at one time promote peace by armament, at another time by disarmament, at one time by insistence on its rights, at another time by a spirit conciliation. To estimate the probability of war at any time involves, therefore, an appraisal of the effect of current changes upon the complex of intergroup relationships throughout the world.
