The nuclear threat that preoccupied Bertrand Russell receded into the background during the Vietnam War. After that war's end in 1975, the risk of a nuclear confrontation between the superpowers again became a major concern.

This issue came in for sustained moral analysis in Douglas Lackey's Moral Principles and Nuclear Weapons (1984) and Steven P. Lee's Morality, Prudence, and Nuclear Weapons (1993). But considerable philosophical interest focused more narrowly on so-called paradoxes of nuclear deterrence. Herman Kahn had spoken of "rationality of irrationality" strategies in On Thermonuclear War (1960). The question was whether it is rational to threaten to do the irrational (wage all-out nuclear war). The strategy of Mutual Assured Destruction (MAD) seemed to presuppose that it is, since it rested on the threat of massive retaliation in the event of a major nuclear first-strike. The moral version of the paradox, explored by...