In truth, in contemporary usage, realpolitik has become interchangeable with “realism” or “realistic.” Simply speaking, it denotes an unflinching and nonideological approach to statecraft and the primacy of the raison d’état. It involves an intuitive suspicion of grandstanding and moralizing on the international stage. In theory, it most closely resembles Morgenthau’s contention that a nation could not “escape . . . into a realm where action is guided by moral principles rather than by considerations of power.” More recent versions of this creed include the neorealist theories advanced by the prominent political scientist Kenneth Waltz, who died recently. Weighty disputes between the champions of liberal institutionalism, rational-choice theory and realism continue to dominate the international-relations field. But it is realism that holds the oldest pedigree and attracts the most ire.

The Frontline Diplomacy archive demonstrates that usage of realpolitik peaked in the 1970s in the Nixon-Carter era. About half of diplomats viewed it positively, and about half used it unfavorably, as something with which they preferred not to be associated. By the 1990s and with the fall of the Soviet Union, perspectives were changing. In 1991, at the end of the Gulf War, a provocative editorial in the Wall Street Journal suggested that the power of twenty-four-hour news television presented a serious challenge to traditional notions of realpolitik. “We recognize that there are significant dangers in trying to create a foreign policy that must incorporate the imperatives of national interest, a common national morality and the information stream of global communications,” it noted, but “Realpolitik is not so readily separated from national values, from a country’s common idea of itself.”

But in its journey from 1853 to the modern day, it has been purged of much of its original meaning. It has become a label or a badge of identification. In that sense, the hand-wringing about realpolitik is, as much as anything, part of an internal monologue in Western liberalism rather than a fully developed view of world affairs. For both its critics and its advocates, it is used to denote a philosophical disposition—an instinct or an inclination—rather than a hardheaded way of analyzing political circumstances on a case-by-case basis.

President Obama’s imaginative use of Reinhold Niebuhr’s work—the subtle strains of which crept into his Nobel Peace Prize speech in 2009—to explain his liberal realism does not, in that sense, represent the true spirit of realpolitik. It is, like much before it, an attempt to square the circle—to articulate an intellectually coherent worldview. Like much of the scholarly practice of international relations, this is theology rather than realpolitik.

WHAT THEN, would Rochau have made of all this? Going back to his original definition, it appears that much of what masquerades as modern realpolitik has strayed quite far from the original essence of the term.

The first thing to note is that he was an enemy of lazy thinking. He would have been unimpressed with those versions of realism that resemble a knee-jerk reaction that responds to idealism with a roll of the eyes and retreats to its own set of tropes and doctrines.

Realpolitik does “not entail the renunciation of individual judgement and it requires least of all an uncritical kind of submission,” he wrote. It was more “appropriate to think of it as a mere measuring and weighing and calculating of facts that need to be processed politically.” Above all, it was not a strategy itself, but a way of thinking: an “enemy of . . . self-delusion” and “the misguided pride which characterises the human mind.”

What Rochau was attempting to articulate was not a philosophical position but a new way of understanding politics and the distribution of power. “Experience has shown that treating it along abstract-scientific lines, or on the basis of principles is hardly useful,” he wrote. One had to contend “with the historical product, accepting it as it is, with an eye for its strengths and weaknesses, and to remain otherwise unconcerned with its origins and the reasons for its particular characteristics.”

Here, once again, his work is distinct from the Renaissance statecraft of Machiavelli because of its attempt to incorporate the conditions of modernity into his analysis. Sovereignty was not the natural property of God, the king, the people or the aristocracy. It was simply a reflection of the balance of different societal forces. The best forms of government were those that mediated between them most effectively; for this observation Rochau was indebted to the Scottish Enlightenment, Edmund Burke and the French social theorist Charles Fourier. In the race among nations, the most successful state would be the one that harnessed the energies and industry of its most productive classes to the cause of the nation. By this he chiefly meant the middle classes, by virtue of their “education, wealth, entrepreneurial spirit, and appetite for work.” In the Renaissance era it had been easier to suppress new societal forces that challenged the authority of the state, but the “increased mobility of the more recent centuries” had made this impossible.

At the same time, however, modernity also presented social and political forces—such as sectarianism or ignorance—which also had to be taken into account. A true realpolitiker could not ignore “those latent forces of habit, tradition and sluggishness” such as “poverty, lack of knowledge, and prejudice” and even “immorality.” Here again, modernity intervened. The “great masses,” too, which “formerly appeared only in exceptional situations in the political arena,” were now an established fact of political life.

Above all, however, in a lesson that modern realists often miss, Rochau refused to dismiss the power of ideas and ideology. “Things like bourgeois class consciousness, the idea of freedom, nationalism, the idea of human equality are completely new factors of social life for many of today’s states,” he wrote, and good policy should not “deny these forces the appropriate recognition.” Such manifestations of “public opinion,” as Rochau called it, “can be potentially very influential and a force that even oriental despotism has to bow to.”

Indeed, it was as a theorist of public opinion that Rochau was perhaps at his most original. He painstakingly laid out different gradations of it, in ascending order of importance. In the first instance, he believed that the “feeble self-conscious opinion of the day is not entitled to claim political consideration,” as it was merely fleeting and unfocused. From this starting point, however, the more “consolidated it becomes, and the more it transforms itself into a firm conviction, the more important it becomes for the state.” The most important expression of public opinion was “Volksglaube” (popular belief), which should always be treated with “care and protection, not blandishment.”

While the popular belief was the highest “peak” of popular opinion, the zeitgeist was its broadest foundation and a central component of realpolitik. The zeitgeist amounted to the “consolidated opinion of the century as expressed in certain principles, opinions and habits of reason.” An opinion transformed itself into the zeitgeist to the extent that it stood the test of time. And the zeitgeist represented “in all circumstances the most important influence on the overall direction of politics.” For a state to “enforce its own aims in defiance of the zeitgeist” was to court serious trouble.

Realpolitik, therefore, was much more than raison d’état. In fact, Rochau made this distinction clear: “Statecraft, as its name suggests, is nothing more than the art of success, applied to the specific ends of the state.”

Realpolitik was about the art of politics in the post-Enlightenment world. He wrote in an age of mass ideological awakening, economic transformation, social upheaval and international rivalry. The job of statesmen was not to remain studiously aloof from these forces but rather to manage and mediate them. For Rochau, too, patriotism and nationalism were not delusions and distractions from raison d’état but one of its most effective tools. A shared sense of national purpose was a “natural conciliatory force” between conflicting parties within a state. This was why “human judgement has been very firm regarding the view that it is the utmost sacrilege to question the national spirit (Nationalgeist), the last and most valuable guarantee of the natural order of society.” Any policies designed to break this spirit, or ignore it, “thereby descend to the lowest ranks of despicability.”

Most importantly, Rochau was a critic of utopianism, not idealism. As befitted a man of the Enlightenment, he understood that ideology played the “role of a harbinger and trailblazer of events.” “Realpolitik would contradict itself if it were to deny the rights of the intellect, of ideas, of religion or any other of the moral forces to which the human soul renders homage,” he wrote. The political importance of ideas was not dependent on how rational or noble they were. On the one hand, it was common that “the most beautiful ideal that enthuses noble souls is a political nullity.” When it came to “phantasms” like “eternal peace,” international fraternity and equality, with “no will and no force” behind them, “Realpolitik passes by shrugging its shoulders.” On the other hand, he noted—casting his eyes to the socialist movement emerging in Germany at the time—“the craziest chimera may become a very serious realpolitical matter.”