To give the human race much chance of survival, considerable co-operation may be needed. When dealing with selfish people, one way of encouraging co-operation is to point to the benefits they could expect from it. Another is to use threats. Both ways involve problems in decision theory, perhaps best illustrated by the case of trying to prevent nuclear war. (This will be a very brief chapter, avoiding a host of technicalities.) 1
Suppose two nations seem to be moving towards nuclear war. Each might see much reason to strike first, so as to destroy many enemy missiles before they could be launched.
A ground for not striking first is the hope of remaining in the situation in which no nuclear bombs are exploded by anyone. Yet this can raise ‘prisoner’s dilemma’ problems.
A ground for not striking second is that one’s nation may have been so nearly annihilated that there remain no benefits to be had by striking. This raises problems of whether it can be right to carry out acts of revenge.
Say that two superpowers—call them Oceania and Eurasia—have constructed huge nuclear arsenals. For the two of them taken