Intellectual stances in international relations often come with “ism” as a suffix, a choice of a core term (real, constructive, liberal, rational) and sometimes with a prefix or modifier—classical, neoclassical, structural, neo, hyper, and post, among others. And although many decry “ism” or paradigm wars in the field, contributions are repeatedly posed in terms of pitching, if not advancing, one perspective over others.

Jonathan Kirshner describes his new book, An Unwritten Future: Realism and Uncertainty in World Politics, as “the articulation and application” (p. 2) of classical realism. And any exercise of intellectual mapping and self-identification must have an other against which to juxtapose, and here they are structural realism and hyper-rationalism, respectively.

Kirshner begins with an exposition of realism’s “core principles,” (pp. 13ff) that are almost all to be found in Thucydides. Scholars will find them familiar: the consequences of an anarchic world, the resulting need to be attentive to the distribution of power, the constant dynamic changes in the distribution of power, the continuity of a pessimistic view of humanity, that individuals are the ultimate actors in world politics and thus their motivations matter, that nevertheless the unit of analysis is the group and its political goals, the inevitability of political conflict, the never-ending character of politics, and the emphasis on uncertainty and contingency which implicate a “wide and unpredictable range of the possible.” Some or all of these are widely accepted tenets of realists (and even of others who develop their arguments as adjuncts, adjustments, and modifications of realism). But classical realism has more to it, and that is provided by Thucydides’s additional emphases that include purpose as well as power, the importance of regime type and national character, of diplomacy and leadership and hubris. These aspects of realism are then shown to be evident to some degree in the work of Machiavelli, Hobbes, Clausewitz, and Burke, as well as in the works of twentieth-century realists including, E.H. Carr, George Kennan, Raymond Aron, and Robert Gilpin.

Having laid out a view of classical realism that would seem to constitute a kitchen-sink eclecticism that includes every possible explanation for every possible outcome, Kirshner proceeds to contrast it with structural realism and hyper-rationalism. He recognizes that classical realism and structural realism share many facets including the significance of anarchy, the importance of the balance of power and national interests, and the centrality of politics. But, he argues, classical realism adds the indeterminacy of structure, the centrality of history, the importance of purpose as well as power, all of which imply that domestic politics and ideational variables are essential to explanation. He then proceeds to attack hyper-rationalism, epitomized by the rational explanations for war argument. The dissections are both apt and to some degree attacks on exaggerated characterizations of alternative approaches.

This is followed by two proofs of concept: extended historical discussions of explanations for British appeasement in the 1930s and U.S. involvement in Vietnam (and Iraq). The former, Kirshner asserts, cannot be explained without understanding the role of ideology, which is ignored in structural realist arguments. This confident assertion, based on secondary sources, reflects only some of the historiographic debate about appeasement. Yet there are historians who have provided explanations for British policy without reference to ideology. Indeed, given the contested historiographic debates that exist for many of the cases discussed in this book, and given the book’s own emphasis on unknowability and contingency, one wonders about the certainty with which historical explanations are provided. In a similar vein, U.S. military intervention in Vietnam in the mid-1960s (and the war against Iraq in 2003) cannot be explained without the importance of hubris, something that is outside of perspectives other than classical realism.

Kirshner proceeds to discuss the limitations of classical realism, though most are not about its analytic limitations and are general issues in the social sciences. Classical realism, as is the case for other perspectives, cannot address issues of morality, must separate prescription from description, and provides little by way of policy advice. The only analytic limitation discussed is that of the fuzziness of an essential construct for classical realism: the national interest.

Kirshner then turns to his specialty, international political economy and its role in classical realist analysis in contrast to that of structural realism. The chapter is a virtuoso discussion of the evolution of arguments about the role of international economic relations in international politics.

Next he addresses contending views of the rise of China and its implications for international politics (and policy). The reader is first treated to an evisceration of John Mearsheimer’s argument in The Tragedy of Great Power Politics and an annihilation of Graham Allison’s characterization of Thucydides and the historical record in Destined for War. Kirshner’s classical-realist inflected take is similarly “pessimistic about the implications of China’s rise for international stability” but suggests “the need to find ways to accommodate that rise” (p. 198) and to recognize the primacy of politics and history (though oddly done in an extended discussion of Japan in the 1920s and 1930s rather than contemporary China).

The concluding chapter brings the strands of the approach together and includes digressions on civilizational collapse and the failure of France in 1940 to rally to its own defense, and the historical basis as well as contested nature of the development of an American order with purpose following World War II. It ends with a purported view of what a classical realist foreign policy for the United States would entail, though the entire book until then would commend caution in accepting any of the suggestions as uncontested implications of the perspective. Finally, it notes that the United States may be incapable domestically of pursuing a coherent foreign policy.

The book is a lawyer’s brief on behalf of classical realism, finding that its valuable insights are only partially available in contending approaches, and thus unsparing and caustic in its criticisms of others’ omissions and limitations. Its pitch offers a particular view of the social scientific enterprise: one not intended to “describe, explain, and predict,” but one intended to “describe, explain, understand, and anticipate” (p. 53). As plainly put in the book’s title, the future is unwritten and therefore possibly anticipated but unknowable and unpredictable, not even in a probabilistic sense. And since the book’s focus is on understanding the specific foreign policy of specific states at specific times, a classical realist perspective is one in which almost any foreign policy is possible, and in which all imaginable factors can play a role and must perforce be included in any analysis. Looking at historiographic disputes over the origins of past wars, one is left to wonder what the scholarly field of international relations possibly has to offer. Classical realism may provide excellent analysis but includes all variables and can only provide description and perhaps understanding in retrospect, but for which explanation will remain contested and illusory. It offers a picture in which everything is a possible explanation and in which everything is a possible outcome.

The book includes well-worn and familiar observations and criticisms, as in the roots of structural realism in the industrial organization literature on market structure. But it also has unfamiliar and contestable observations, as in the linking of the rational explanations for war argument with rational expectations theory in macroeconomics, in which criticisms of the latter become central to a critique of the former.

The book is erudite and contentious. It is the kind of work that could only be written by a senior scholar building upon and summing up a long, distinguished career’s work in the field. It is written for international relations scholars already steeped in the perspectives of the field (there are exceptions such as the discussion, complete with supply and demand curves, of the impact of a change in price for the supply of ketchup in which the point is simply that as the price of ketchup goes up the demand will go down, but that economists cannot predict exactly which people will continue to buy ketchup at the higher price and which people will not). Its views and astonishing breadth of knowledge are on display not only in its wide-ranging historical and exegetical text but also in its extensive footnotes with their numerous analytic observations. Knowledgeable readers may be puzzled by some of its characterizations—even the most ardent advocates of classical realism will find some things with which they disagree. Yet all will be dazzled by the range of the learned discussion.

Three analytic issues are at the core of this book and its contention. First, is the field of international relations largely focused on describing and explaining the specific actions of specific states at particular times? It is possible to argue that the field is not limited to just that enterprise, and thus the injunctions and critiques in the book are more limited in their import. Like economists interested in the implications of price shocks on demand, international relations scholars can assess the implications of shifts in the balance of power even absent an ability to predict the actions of any one state. Second, even when engaged in explaining specific historical policies, is the field’s best strategy to treat all outcomes as equally probable (this is implicit in the books argument that probabilistic explanation is impossible) and all factors as possible explanations? Does the nature of the field preclude prediction and generate utter unknowability? The author’s articulated answer is yes, but slippage is to be found throughout the book. The repeated discussions of when hubris arises in the actions of great powers looks very much like a prediction drawn from the modal results of historical cases. Indeed, Kirshner reproduces a prescient prediction that he made in 2003 that the war “was very unlikely to achieve, and in fact would probably undermine, the broader political objectives for which it was fought,” and in time “a fatigued and impatient America” would eventually distance itself “from the chaos that ensues” (p. 121). All of us make predictions based on a knowledge of the modal and average case, and we are also interested in aggregate outcomes even when specific individual ones are uncertain.

This is the best defense of classical realism as an approach to international politics on offer, providing both textual exegesis of key scholars delineating and applying the perspective as well as historical applications ranging from the ancient world to contemporary times. It takes its place on the bookshelves of international relations scholars alongside major works proposing the other “isms” that populate the field.