国際システムの動態と安定

世界システム論

抄録

The aims of this paper are: to construct a general model regarding choice between war and peace; to develop a set of propositions regarding the stability of the international system; and empirically to test some of these propositions. The. model, which is constructed on the basis of the expected utilities of war and diplomatic means, provides us with three general factors which affect the stability of the international system: (a) the power structures which determine the probability of winning in war; (b) the level of conflict which is measured by the benefits that would be obtained by victory; and (c) the level of diplomatic harmony which is measured by the highest expected utility of the non-war alternatives. The bipolar stability can be obtained, according to our model, by maintaining the bilateral power parity to reduce the probability of winning in war to a fifty-fifty chance so that the expected utility of war becomes zero; the unipolar stability can be obtained by lowering the level of conflict and/or raising the level of diplomatic harmony; and the multipolar stability can be obtained by manipulating multilateral power equilibrium and by maintaining a medium level of conflict and diplomatic harmony.
Though it is difficult directly to measure the level of conflict and diplomatic harmony, the conditions —ups and downs— of the world economy are believed to affect these levels. The relative potency, and the interaction effects, of the power structure and economic conditions on the occurrence and severity of major power wars are empirically examined during the period between 1495 and 1975 by utilizing the Levy's and Goldstein's data. The major findings are: while the power structure factor has a strong influence on the occurrence of war, the economic condition factor has a significant effect on the severity of war; and the interaction effects of the two factors have a large, though statistically not significant, influence on both occurrence and severity of major power wars.