Will there be “but one heart to the globe?” asks Walt Whitman in a poem that provides an epigraph in Mark Mazower’s new book, Governing the World: The History of an Idea. At the center of this expansive work is the question of how Americans and Europeans have imagined the world, its peoples, and its nations. Is there but one global identity, as Whitman surmises? Are the world’s peoples the focus of global politics, or should nations be privileged in international affairs? Do values and culture, or degrees of civilization, set nations apart? These questions inform global affairs over time. This history matters, Mazower argues, as “we find ourselves… in a hierarchical world in which some states are more sovereign than others.”

Power also matters: For Mazower, dominant nations come to play a role in defining the world. He embeds his narrative in the development of familiar institutions, such as the United Nations, and is especially compelling when he reveals lesser-known stories like the development of common units of measurement, presided over by social scientists in the West. This ambitious and largely convincing account falls short, however, when the author turns to contemporary matters. Disappointed that international law does not adequately constrain American war efforts, he misses an important turn in modern conflict: the way that law itself has been reimagined as a weapon of war.

To make the point that the history of ideas matters to contemporary policy-making, Mazower opens the book with a young Henry Kissinger writing about the Concert of Europe. The Concert, an innovation in global politics in 1815, enabled Austria, Prussia, the Russian Empire, and Great Britain to work together in an effort to contain the revolutionary spirit of France. Emphasizing order over rights and liberty, they saw themselves as speaking for Europe as a whole. Their accord legitimated intervention in the domestic affairs of other European nations. “[R]ight at the start of the history of international institutions,” Mazower writes, “we find states and politicians arguing over the limits of ‘the government of the world.’ ” As for Kissinger, his dissertation topic provided him with “a lesson of enduring value” for America: “What long-dead European aristocrats… could teach the United States was how to constrain a revolutionary superpower—for France read the USSR—and bind it into the rules of the international game.”

A leading scholar of twentieth-century European history at Columbia University, Mazower is at his best in Governing the World when he illuminates the way European and American understandings of global politics unfolded. Works on the history of world governance most often focus on diplomacy, international conflict, and the establishment of institutions like the United Nations. The history of ideas usually appears through the biographies of important leaders like Woodrow Wilson. But Mazower places ideas about the world and its governance at the center of the story, with individuals as the carriers of certain concepts. This makes an otherwise familiar story new and exciting. The author’s central thesis unfolds gradually and implicitly, and his narrative beautifully expounds the shaping role of ideas over time. But Mazower does not share enough of his own thoughts, withholding a more explicit theoretical analysis. That absence might have been intended to make the book appealing for a broad readership—and it is a wonderful read—but it also undermines the book’s power.

The very word “international” emerged in the 1780s, coined by philosopher Jeremy Bentham to distinguish between internal laws and what was then called “the law of nations.” Ideally, for Bentham, international law would promote “the greatest happiness of all nations taken together,” and would be crucial to maintaining peace. Before long, Mazower writes, “ ‘international’ had already become an -ism, a radical project,” which developed along with the rise of representative government. By the mid-nineteenth century, “[i]nternationalism, in its modern sense as a movement of cooperation among nations and their peoples, was moving from the realm of marginal ideas into the mainstream, while monarchy itself was obliged to accommodate itself to the era of large electorates and parliamentary power.”

Later in the century, migration, colonization, and technological advances such as steamships and the telegraph helped forge a sense of the world as an interconnected whole. But imagining the world as one entity was only one step in a vision of world governance. The question of whether nationalism aided or undermined global politics was tackled by Italian revolutionary Giuseppe Mazzini, who sought Italian national unity and promoted European rule by the people rather than monarchs. If Mazzini has been largely lost to history, Mazower resurrects him as a central figure, and as Woodrow Wilson’s muse. Mazzini’s vital contribution was the idea that nationalism should be a defining feature of international politics—that international politics should happen between and among democratic nation-states rather than more directly among the world’s peoples. We are first introduced to Mazzini long after his death, as Wilson pays homage to his statue in Genoa on his way to Paris in 1919, where he would help to create the League of Nations. Mazzini is a seminal figure, Mazower writes: “[H]is vision of a world that is at peace because it has been transformed into an international society of democratic nation-states proved long after his death to be enormously influential.”

Mazzini reappears throughout the book, in part as a reminder of his nineteenth-century vision that democratic nations should be the principle units of global politics. He serves as a stand-in for Mazower’s fundamental, if often implicit, methodological point: that ideas do work in the history of diplomacy, and that our very understanding of the world emerges from specific cultural and political moments.

Ideas can foster liberation—but as Mazower reveals, humanitarian efforts can also be double-edged. A stark example of this was a late-nineteenth century effort to codify international legal practice, and especially the attempt to use law to humanize warfare. These developments laid the basis for the laws governing armed conflict that we have today.

International law was codified during an era of colonization, in which populations thought to be “savage” were claimed by the “civilized” world. In this context, “civilization” became a standard against which peoples could be judged. The first Hague Peace Conference was held in 1899, 15 years after European powers had divided Africa among themselves at a conference in Berlin. The conference attempted to limit and civilize warfare by protecting civilian populations in occupied zones. Mazower explains: “The legal doctrine of military occupation itself was intended to regulate a provisional state of affairs in which one sovereign’s forces ran the territory of another without prejudicing the latter’s claims to ultimate control.” But what of colonized peoples who were also occupied? The law of military occupation “did not apply to ‘savage peoples,’ since they lacked a recognized sovereign.”

Because of this, Mazower writes, “the spread of international legal arguments in diplomacy helped to remove the protection of the law from everyone else.” It was not just that “savage” peoples, including Africans and Asians under colonial government, were outside of the law’s protection. This dichotomy also affected supposedly more civilized forces. During the Chinese Boxer Rebellion, the German military treated the Chinese “as a legitimate object of vengeance.” In that way, “law itself looked like a rationalization of plunder, a world made free for the mighty to rob while claiming that justice was on their side.”

In a fascinating chapter, Mazower illustrates the way that developments in science and technology facilitated world governance. Arthur Schuster, a prominent German-born British scientist, wrote in Nature in 1906 that science had a “civilizing” effect and could expose the artifice of political boundaries. “When diplomacy fails,” he argued, “it will fall to the men of science and learning to preserve the peace of the world.” New professional organizations emerged, focused on the goal of developing common standards of measurement. Mazower notes that “[t]he gold standard was an ideal of monetary internationalism,” and an international conference in 1875 sought to unify weights and measures through the adoption of the French metric system. Especially important was the effort to harmonize the keeping of time, which would eventually lead in 1946 to the International Meteorological Organization establishing Greenwich Mean Time as the universal standard. The close of the nineteenth century “saw the emergence of an entirely new kind of institutional presence in international life.” Statisticians, engineers, seismologists, and other experts held international congresses, collected data, and sought to map and measure features of the world. Standardization would have its limits, as every international traveler knows when she packs an adapter for electrical outlets. But the organizational infrastructure developed in the late nineteenth and early twentieth centuries would endure. Bodies like the International Organization for Standardization would perpetuate the underlying idea “that policy is best left to technical experts who know no nationality but that of humanity.”

For Mazower, the proliferation of international organizations was significant for world governance, as this form of organization became “an established feature of the modern political landscape.” The importance of these groups extended beyond their form, however. In the midst of the move toward standardization was a struggle over what standards to adopt, revealing different visions of how to understand the world. In the field of seismology, for example, disagreements over how to measure and compare earth tremors raised the most fundamental question of all: Does simply examining the world require organizing information into arbitrary man-made categories? As Mazower asks, “[W]as the classification of data dictated by the very structure of the world or was it in fact a matter of pragmatic choices, dictated by the purposes for which data were collected and the kinds of models that were generated by the scientists themselves?”

Mazower elaborates on the way values affect the presentation of data about the world in a chapter about Reagan-era economics. Amid a story of layered world governance, with nongovernmental organizations (NGOs) and global economic institutions like the International Monetary Fund and the World Bank playing essential roles, Americans asserted influence through “the successful spreading of… ideas about what knowledge was.” American- and English-trained economists were central to this story. “Entering the IMF and the World Bank in the 1980s, they were rational-expectations revolutionaries who based their prescriptions on in-house templates couched in the language of the highly formalized mathematical models that the profession was coming to prize,” he writes. Deep knowledge about different countries didn’t matter; it was an “exogenous variable.” The group developed a “new dogma [that] assumed that universal virtue resided in the market.” Convinced about the importance of their ideas, they worked to put them into place, pushing privatization and deregulation. The ultimate consequence, Mazower argues, was “an extraordinary transformation of property relations throughout the world. With startling speed, water, electricity, coal, trains, and buses were among the nationalized industries sold off.”

Internationalism became institutionalized during the twentieth century with the creation of the United Nations, but global organizations became “a vital instrument for Washington in its pursuit of global power.” Though Washington policy-makers sought control of international institutions, Mazower argues that it wasn’t out of mere cynicism—many honestly believed “that the values of American liberalism were identical to the interests of the world writ large.” Indeed, while Americans could never completely control multinational institutions, “the blisteringly fast emergence of American global power after 1945 is unimaginable” without them.

The emergence of NGOs like Amnesty International would show, however, that there was still a role in global politics for ideas like human rights, “that activism could make a difference.” But then the U.S. government backed the National Endowment for Democracy, a so-called NGO supporting a neoconservative vision of human rights, and the line between government and private advocacy groups was blurred.

After a searing tour of the way humanitarian ideas come to serve powerful interests, the lesson Mazower ultimately offers at the end of the narrative sounds like a conventional liberal complaint: The Obama Administration’s embrace of drones and targeted killings, coupled with the belief that humanitarian norms can be programmed into robotic warriors, seems to unravel a Benthamite view of law as enabling global well-being. Instead, “the appeal to law has become a vocabulary of permissions, a means of asserting power and control that normalizes the debatable and justifies the exception.” An older vision of international law “continue[s] to be taught as though it still has meaning. But it no longer carries much conviction, and the idea of a law binding upon all states and those governing them seems as far away as ever.”

At this point, Mazower seems to back away from his central premise. If ideas and understandings of the world animate global politics—if, that is, international affairs is more than a clash of power and self-interest—how could ideas and values simply lose traction in the present generation? Governing the World is brilliant in showing the way ideas shape institutions and are used by global powers, but Mazower does not provide much of an account of why ideas lose their power in world politics.

Mazower complains that law has atrophied as a restraint on power: “[L]egal arguments are publicized when they are serviceable and buried when not, and this increases the sense of their purely instrumental nature and subordination to the authority of the political.” But there is more to say about the instrumental character of law. Perhaps it has taken on a perverse quality, and we’ve failed to realize it. It’s not just that law is either obeyed or ignored. It is that law is often the place where decisions about warfare and security are made.

An example of this is the infamous post-9/11 “torture memos” that provided a legal basis for inhumane practices by American interrogators. The greatest difficulty with the torture memos, however, was not that John Yoo, the George W. Bush Administration lawyer who wrote them, got the law wrong. It was that legal answers drove too much of the policy.

Jack Goldsmith explains this in The Terror Presidency, his account of his stint as head of the Office of Legal Counsel in the Bush Administration. Goldsmith writes that because President Bush anticipated the possibility of another terrorist attack, he could justify a failure to act only if he had a good reason. “A lawyer’s advice that a policy or action would violate the law, especially a criminal law, was a pretty good excuse,” Goldsmith writes. With the White House understandably driven to avoid another attack, “the question, ‘What should we do?’… often collapsed into the question ‘What can we lawfully do?’… It is why there was so much pressure to act to the edges of the law.” In such an environment, with the President and his staff committed to go as far as they could, law set the boundary of action, and arguments about law were volleys in a struggle for power. For Goldsmith, it was “strategic lawfare.”

Goldsmith’s use of the concept “lawfare” gets at something more important than the usual disagreements among lawyers. Retired Air Force Major General Charles Dunlap Jr. described it in an influential essay in November 2001 as “the use of law as a weapon of war,” or the use of law “as a means of realizing a military objective.” Law as a weapon, for Dunlap, can be used for good or for ill. An enemy might engage in lawfare by placing military targets in heavily populated areas, so that if they were bombed, an outcry would ensue over the unlawful killing of civilians. This might seem to turn law into just another weapon of war, instead of a restraint. For Dunlap, law nevertheless restrains force by bringing engagement with humanitarian norms into discussions of military strategy. Following from this, law is an important aspect of military training, with members of the JAG Corps schooled in Operational Law, which covers legal rules of conduct on the battlefield.

Following the path of lawfare from the corridors of power to ground-level decision-making by soldiers, we can also discern the path of ideas, from policy argument to implementation—in this case at the end of a gun. Law in this context is not simply an idea that can occasionally constrain. It has become a technology of warfare—a tool that enables killing. A consequence of this, legal scholar David Kennedy writes, is that “violence and injury have lost their author and their judge as soldiers, humanitarians, and statesmen have come to assess the legitimacy of violence in a common legal and bureaucratic vernacular.”

When law has become a place where decisions get made, and the answers to questions like “Should we engage in surveillance?” and “Should we bomb a target?” are legal ones, law displaces other questions, such as “What furthers the nation’s long-term interest?” and “What is moral?”

How far down this road we have gone is apparent in the jarring discussion of the role of law in robotic warfare. Scholars argue about how well we can code international humanitarian law into computer software, so that self-directed robots engaged in warfare would be programmed to abide by legal limits. In this context, law is not so much an idea as a military technology. It does not aid judgment, but diverts our attention from morality, diplomacy, humanity, and responsibility in the use of force, and especially from the bloody mess left on the ground.

At the end of Governing the World, Mark Mazower seems almost nostalgic for the nineteenth-century world he describes, in which ideas had power and shaped institutions. He wishes that law would play more of a role in the governance of armed conflict. But the ideas informing international humanitarian law have not run out of power. Instead, they are encoded into software. Mazower is right to suggest that ideas are an essential part of the governance of the world. But there is more to say about their double-edged quality. They might inform the way a Woodrow Wilson, or a young Henry Kissinger, imagines the world. But then they become the language, and vessel, of power.