Two arguments have traditionally been made about the effects of proliferation on the likelihood of nuclear war. One argument claims that proliferation increases the likelihood of nuclear war; the other claims that proliferation reduces the likelihood of nuclear war. This article shows that, in fact, both of these arguments are logical and probably true some of the time. The key factor that decides when one argument is more valid than the other is the degree to which nuclear powers can deter other nuclear powers. Because the conditions necessary for stable deterrence can vary systematically, it is possible to define when proliferation is a threat and when it is an asset. Moreover, using these principles, the article analyzes the effect of previous cases of proliferation on the likelihood of war, and shows how a compromise policy for dealing with proliferation can best be determined.
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