The starting point for Christian Davenport, Erik Melander, and Patrick Regan’s very welcome study is what they regard as the failure of much scholarship on peace to conceptualize and operationalize peace adequately. Gary Goertz discussed this problem in these pages as recently as March 2020 (“Peace: The Elusive Dependent Variable and Policy Goal,” Perspectives on Politics 18 [1], 2020) but the problem has a long lineage. The value-added of The Peace Continuum is the authors’ efforts to move beyond a mere articulation of the problem and propose various approaches to redress it.

Much scholarship on peace, within or between states, the authors observe, is not fundamentally about peace but about armed conflict or, more precisely, the absence of armed conflict. Although this observation may be consistent with a minimal conception of peace, commonly known as “negative peace,” too often scholarship reduces peace to this minimal conception. Such reductionism masks a wide variety of conditions that represent the rich empirical reality of peace. Peace understood as “not war” has utility—for quantitative analyses of armed conflict especially—but it conflates the character of peace as varied as that which prevails in Sweden, for instance, with that of North Korea. Both countries (at present) would qualify as states at peace by conventional measures such as those employed by the Correlates of War Project or the UCDP/PRIO Armed Conflict Dataset, but the quality of peace in each case differs dramatically when one takes into consideration forms of violence other than armed conflict, such as torture or aggressive policing.

Other distortions arise, the authors maintain, as a consequence of the “conflict centric” (p. 17) nature of peace studies, notably a tendency to focus disproportionately on peace in the immediate aftermath of violent conflict, as opposed to enduring peace within and between states, and a corresponding lack of attention, theoretical and empirical, to the conditions that generate peace and prevent the eruption of violent conflict.

To enrich our understanding and analysis of peace, the authors propose studying peace as a continuum, from “not war” in its minimal manifestation to what the authors call “political mutuality” in its fullest expression, which entails “a quality of respect and fundamental good will between relevant actors” (p. 3). The authors are not the first to suggest the importance of conceiving of peace in spectral terms. Indeed, they draw some inspiration in this regard from Gary Goertz, Paul Diehl, and Alexandru Balas’s “peace scale” (from “severe rivalry” to “security community”) for gauging the peacefulness of relations between states. Equally, they might have mentioned the work of Paul Richards (“New War: An Ethnographic Approach,” in No Peace, No War: An Anthropology of Contemporary Armed Conflicts, edited by Paul Richards, 2005), who urged scholars to think of peace specifically in terms of a continuum. The more nuanced and thus more accurate analysis of the quality of peace that can be achieved with an enlarged conception of peace plotted along a continuum is apparent in a number of cases that the authors discuss throughout their book, including the United States and Rwanda.

The obvious difficulty with proposing any expanded conception of peace is that there is no consensus among analysts on the characteristics of “positive peace”—a difficulty that has long hampered scholarship and has led, as one consequence, to a sometimes significant degree of incommensurability among analyses of peace. Compare, for instance, Roland Paris’s positive assessment of peace in Eastern Slavonia/Croatia (At War’s End: Building Peace after Civil Conflict, 2004) with Peter Wallensteen’s comparatively negative assessment of the same, which turns on the salience of “dignity” as a requisite factor (Quality Peace: Peacebuilding, Victory and World Order, 2015). It becomes clear from Davenport, Melander, and Regan’s insightful survey of the relevant literature that the many notions of peace are too diverse conceptually to be mutually inclusive. The authors seek to remedy the conceptual inadequacies by articulating what they consider to be the criteria for a good definition of peace: notably, that it should be graduated and multidimensional but not too encompassing, that it should be sensitive to violence in its manifold forms, that it should be grounded in theory about conflict, and that it should be capable of being operationalized across a large number of observable units.

But how exactly should the concept of peace be operationalized? Here is where the book is particularly interesting. In three separate chapters, each of the authors puts forward his own approach to the conceptualization and measurement of peace. Each approach is distinct but arguably satisfies the criteria on which the authors agree. Patrick Regan proposes what he calls a “perceptual approach” in which peace (“when no group has an incentive to change the status quo by resorting to violent methods”) is an “equilibrium condition” (p. 79) that is weakly or strongly maintained depending on the level of satisfaction among members of society with the rules and practices that underpin it. How does one gauge the disposition of a society’s members? Regan proposes black-market currency exchange rates and bond prices as proxy indicators. The risk that individuals are willing to take to pay for foreign currency or bonds, he argues, is a reflection of fundamental satisfaction or dissatisfaction with the status quo. There is certainly novelty in this approach, but notwithstanding the impressive supporting evidence that Regan offers, quite a leap is required in assuming that individuals’ willingness to engage in criminal black-market behavior is indicative of a propensity to resort to violence and thus disturb the peace.

Erik Melander proposes what he calls a “procedural approach” to peace, which places emphasis on the existence and proper functioning of procedures within a society for resolving political conflict. For Melander, peace should be measured in terms of the degree of respect for individual physical integrity, the extent to which consensual decision making (as opposed to political compulsion) is practiced, and how well equality values are enshrined, specifically respect for women’s social rights. Why equality values and women’s social rights in particular? Melander maintains that acts of violence entail domination, and the greater the respect for equal worth, the less scope there is for domination. The focus on women is justified, Melander claims, because women are affected by the unequal valuation of human worth in every society, whereas other expressions of unequal valuation, such as racism and religious intolerance, are not universally relevant nor, he contends, as inherently linked to militarism. The theoretical justification for this latter choice is questionable: for one thing women may be valued more highly in a society than are religious, racial, and other minorities, and equal treatment of women is not necessarily antithetical to militarism (consider the case of female soldiers in Israel, for instance). Why not a measure of peace that takes into consideration the treatment of women and minorities?

Christian Davenport offers the third and final approach to peace, what he calls a “relational approach.” He defines peace as a condition whereby individual actors exist in a relationship of mutuality (i.e., where there is some degree of shared identity): the quality of that mutuality, as opposed to conflict, can be measured in terms of behavior, organization, language, and values across five levels of analysis: international, regional, national, intranational, and communal. Davenport’s approach has broader application than the other ones in this regard and allows for variation within any given level. However, it is perhaps more taxonomical and less theoretically informed than the other approaches. For instance, how is mutuality to be achieved? Davenport tells us: when “actors who are interested in moving toward mutuality…attempt to create the most facilitative situation they can for their preferred outcome by systematically ‘selecting out’ the factors that go against their favored position and by ‘selecting in’ those factors that go along with or promote their favored position” (pp. 155–56). What Davenport offers is more of a score card than a theory of change.

I have raised questions about aspects of the specific approaches that these authors have adopted, and I welcome their responses. However, these questions should not detract from the enormous value of their work. Their diagnosis of the fundamental weaknesses of peace studies is sound, as are the general characteristics of their response, notably the emphasis on broader, nuanced, and operationalizable conceptions of peace. There is great merit in the way of thinking that these authors are encouraging scholars to adopt. Our research will be more precise, more insightful, and arguably more impactful if we heed their advice.