Campbell Craig has written a well-researched and cogently argued account of the intellectual development of three twentieth-century realists, Reinhold Niebuhr, Hans Morgenthau, and Kenneth Waltz. In the first place, this book succeeds where many academic works fail: Craig does not expect his readers to know the character and history of twentieth-century realism. Instead, in the process of contributing a fascinating new account of the effect that the prospect of thermonuclear war had on the ideas of these three men, Craig also familiarizes his readers with both the prehistory of modern realism and its ideational foundations.

Craig argues that the prospect of a thermonuclear war forced these three realists, all of whom began their careers claiming warfare between states is both an inevitable and inescapable consequence either of human nature (Niebuhr and Morgenthau) or of the anarchic structure of the international system (Waltz), into an abandonment of their absolutist realist doctrine. As Craig writes in the preface, he proceeds "from the assumption that their most important ideas can be better gleaned from what they wrote publicly than from their private correspondence, from psychological analysis, or from an extensive treatment of their particular personal circumstance." (p. xiii) This book is what he calls, rather modestly, a "traditional history of ideas." (p. xiii) But, as a history of ideas, Craig does more than merely chronicle the development and the change in the ideas of these three men. Instead, he tries to show the internal dynamic that guided those changes.

For instance, he shows Morgenthau's evolution from the apparently amoral contention that the "simple and universal lust for power . . . drove international conflict" (p. 57) to his moral differentiation between the character of America's foreign policy during the Cold War and that of the Soviet Union. Thus, in his later thought power politics is no longer a contest between "undifferentiated insatiable hegemons" (p. 61), but between moral good and evil as represented by the United States and the Soviet Union, respectively — a contest the United States could only win if it engaged in the evil of power politics. Craig shows how Niebuhr's thought evolved in a similar manner.

While the treatment of these first two thinkers is fascinating, both for the depth of its insight and for the breadth of its understanding, Craig's argument about the internal dynamic guiding the evolution of their thought remains somewhat unclear. In the first place, Craig attempts to unify all of these thinkers, including Waltz, by showing that the terrifying prospect of thermonuclear war forced them to abandon their realist understanding of inevitable engagement in favor of the "glimmer" or the hope of a world state, or what he calls the "new Leviathan." For all of them, only by creating a world state could we avert the disastrous consequences of the almost inevitable war that would occur between two nuclear states. Whether or not they made this explicit, Craig persuasively argues all three inched closer and closer to such a position. Following this logic, their fundamental arguments changed in light of the prospect of thermonuclear war. They all had been thorough-going realists who recognized that their realism was inapplicable in a world where the stakes were now so much higher.

But, in his treatment of Niebuhr and Morgenthau one finds the presence of a different, somewhat more nuanced, argument. According to this argument, Niebuhr and Morgenthau were never thorough-going realists. Instead, as he says at one point in describing Morgenthau, "theories are devised to serve normative ends." (p. 111) Instead, for them, realist theory served as a strong medicine to shake the United States out of its utopian idealism regarding the character of the rest of the world. Owing much to Nietzsche, Craig shows how these thinkers emphasize the insatiable character of a state's will, in much the way that Nietzsche had shown the insatiable character of man's will-to-power.

Their emphasis on this insatiable desire for expansion would, they hoped, compel the United States to engage in the power politics they thought so necessary for either its survival (Morgenthau) or the survival of civilization (Niebuhr). But, precisely in this underlying hope, they betray an essential contradiction. Their argument makes a universal claim about the nature of political states which attempts to show that the "lust for power" (p. 56) is common to them all. They claim to speak as scientists analyzing the nature of man; but the very reason they choose this emphasis, to awaken America from its idealistic slumbers, betrays a certain assumption about the superiority of the United States. Thus, they implicitly do differentiate between their state and other states. In fact, as their later writing affirms, they prefer the United States precisely because it is a more peaceful, less war-like state than either the Soviet Union or Nazi Germany. That is, it is a state less inclined to pursue the very policies they hoped it would adopt.

According to this argument, it would not make sense to say that Morgenthau and Waltz were forced to abandon their realism in light of thermonuclear war. Instead, it makes much more sense to say that they embraced the change wrought by the prospect of thermonuclear war. The prospect of thermonuclear war gave them a means to achieve the normative end that had always informed their writing: world peace. Before, they thought world peace could only come with American strength in the face of non-peaceful enemies, a strength that could only be possible if America were much more realistic about the character of the world. Now, the prospect of thermonuclear war might frighten all enough to turn toward the world state that could best secure world peace.

Accordingly, it is incorrect to write as Craig does that "Hans Morgenthau and Reinhold Niebuhr each developed a political philosophy that aimed to understand modern political nature and the depth of modern war." (p. 115) It would, instead, be more correct to say that they developed a political philosophy that they hoped would make man transcend modern war and modern political nature.

Given their underlying argument itself, perhaps it is not quite that surprising that a strong moralism informed both Niebuhr and Morgenthau. Unlike Waltz, their realism does not start from an assumption about the rationality of human beings in an anarchic world. Instead, it starts from an argument concerning the irrational will-to-power of human beings and the expression of that lust for domination through state aggression.

Such arguments, precisely in their quasi-Christian emphasis on the sinfulness of man, often betray a lingering hope that, if only he would recognize his sin, man could also overcome it. As Craig nicely demonstrates, Waltz, unlike Niebuhr and Morgenthau, begins not from some sinful violence to which man is prone, but from a structural argument regarding the inevitable response of a rational state in an anarchic world. For Waltz, the conflict between states is a product not of the aggression of man, but a rational response to a world without a higher power to insure that "defection" is punished. Describing Waltz's groundbreaking 1957 paper, Craig writes: "War recurs not because of a normative fault in the behavior of people or nations, but because the structure of international politics possesses no mechanism to prevent it." (p. 127) For Waltz, unlike Niebuhr and Morgenthau, war recurs despite the intentions of human beings. It recurs for amoral reasons as states who seek their survival respond to a system in which there is no higher power to ensure the cooperation of all. Just as Rousseau's stag hunter is "trapped within a system that forces him to act contrary to the common good" and seize the hare for himself despite his initial attempt to cooperate with other hunters, so too in the modern world, "the peaceful intentions of individual leaders or particular states are always outweighed by the structural forces that push nations toward war." (p. 129)

Craig nicely shows how this explicitly amoral scientific approach initially allows Waltz to "solve" the problem of thermonuclear war. "Structural realism offered international relations scholars the opportunity to become authentic social scientists" and by doing so it also "offered scholars the opportunity to put the vexing dilemma of thermonuclear war aside" precisely by requiring them, as scientists, "to dismiss the moral problem of thermonuclear war from their field of study." (pp. 134-35) Thus, in a sense, structural realism seemed to achieve what Niebuhr and Morgenthau's realism had attempted but failed to achieve: a scientific explanation for war between states. In a manner similar to his treatment of the earlier realists, Craig now traces Waltz's "retreat from parsimony" in the later stages of his academic career. He nicely demonstrates that "Waltz's advocacy of the bipolar system, together with his ominous critiques of alternatives to it, reflected his normative interest in the perpetuation of peace between the two superpowers." (p. 155) Unlike an astrophysicist who "does not morally care whether the orbits of Neptune and Pluto intersect or not . . . Waltz does morally care whether bipolarity leads to a stable international order." (p. 155) Waltz could not maintain his scientific stance toward international events for the whole of his career; in his writing, his abiding moral interest in peace won out over the moral neutrality which he had claimed was so essential to the social scientist. And, while Waltz draws back from his predecessors' goal of a world state, he does so primarily for normative reasons: "the political formation of a serious world state is likely to unleash severe and sustained conflict among societies eager to dominate — or avoid being dominated by — that state, leading to a kind of 'international' civil war." (p. 163) Craig attributes this change to the extent to which "normative concerns influence a social science occupied with the question of war and peace in a nuclear age."(p. 155) He concludes by claiming that all three "gravitated toward the normative goal of great-power peace in the thermonuclear age" and "came to reconsider this philosophy [realism] in the face of the overwhelming normative end of great-power nuclear peace." (p. 165) But his argument seems also to have implied something somewhat different. Craig has perceptively shown how all three "gravitated" toward a normative treatment of international relations. But his argument has also implied that none of them were ever as amoral as their initial scientific posture claimed. Thus, Waltz could have maintained the same amoral posture toward thermonuclear war with which he began his career. Unlike Morgenthau and Niebuhr, it was not a new development which would have forced a reconsideration of his basic argument. But the underlying moral concerns that inevitably influence a social scientist, especially one concerned with issues as grave as war and peace, won out over a pretense of neutrality toward the outcome of such questions. Thus, one need not include, as Craig does, the clause "in a nuclear age." Instead, the nuclear age only brought to the surface the morality that inevitably informs any human being investigating questions of such fundamental moral importance as war and peace.