The Square and the Tower: Networks and Power, from the Freemasons to Facebook, by Niall Ferguson, Penguin Press, 563 pages, $30

The imposing Torre del Mangia is a 289-foot tower rising over Siena's city hall. Below, the Piazza del Campo serves as the Tuscan town's market square, civic meeting place, and entertainment venue. Together they form the metaphor in the title of The Square and the Tower, the British historian Niall Ferguson's new book about networks, hierarchies, and how they have interacted throughout history.

How hierarchies operate is not a conceptual mystery. The emperors of Rome, the caliphs of Islam, the autocrats of the Kremlin, the armies of Napoleon and Eisenhower, the corporate managers of General Motors, the bosses of the Teamsters Union: In each case we see a Mr. Big at the top of the tower directing lieutenants, satraps, prefects, and legates, all the way down to the grunts at the bottom. Hierarchies arose at the beginning of human civilization, but the "zenith of hierarchically organized power," Ferguson writes, "was in fact the mid–20th century—the era of totalitarian regimes and total war."

Yet hierarchies do not rule perpetually without challenge. Ferguson argues that since 1446, three disruptive changes have made it increasingly easy for large numbers of people to interact and collaborate over time and space—that is, to network. The first was the printing press, whose output swept across 15th century Europe and then beyond. The next was the 19th century telegraph cable, which allowed messages to flow from London to Bombay in four minutes. (The telephone, the fiber optic cable, and the satellite download dramatically accelerated this revolution.) The third change is the instantaneous communication of the internet.

Networks are obscure, ephemeral, clandestine, acephalous, and potentially subversive, built around nodes connected by "edges" to other nodes in a manner that produces activity without centralized control. As in Ferguson's "square" metaphor, they are flat, dispersed, and operate beneath or apart from a tower-like superstructure. Moreover, networks can be part of other networks—and they can be created, manipulated, captured, and annihilated by hierarchies. The Russiagate scandal, for example, hinges on the idea that the leaders of the Russian hierarchy have supported and manipulated a network of largely autonomous cyber-trolls.

Ferguson produces several examples of hierarchies defeating challenges from networks. Take Lenin and Stalin's relentless crackdowns after the Bolshevik Revolution. Their regime shrilly denounced any dissenting network—the peasant-led Social Revolutionaries, the kulaks, the Cossacks, the Kronstadt anarchists—as counterrevolutionaries, traitors, bloodsuckers, vampires, and "unreliable elements" of the Communist Party itself. Under Lenin, the Bolsheviks carried out as many as 300,000 political executions in just their first two years of power. Stalin's reign was even bloodier, and three of his own secret police chiefs were eventually taken out and shot. Once the all-powerful Communist Party became established, few Soviet citizens dared to belong to any unauthorized network.

In discussing these events, Ferguson exhibits an enormous range of historical knowledge. The people parading across his pages include Spanish conquistadors, Malayan guerrillas, the Swiss mathematical prodigy Leonhard Euler, Admiral Wang Hong, the Bavarian Illuminati, Hitler and his gang, Nelson Mandela, George Soros, Paul Revere, Henry Kissinger, Mohammed Atta, the Tuscan painter Ambrogio Lorenzetti, and hundreds more.

These vignettes can be fascinating but sometimes run aground. Many of the book's 60 chapters appear to be instances of an author taking the opportunity to mention something of interest from his research, whether or not it readily illustrates his theme. He devotes one chapter, for instance, to the origin and social habits of an elitist Oxford/Cambridge in-group called the Conversaziones. The historian spends a remarkable amount of writing describing the sexual peccadilloes of the Apostles, as they called themselves. The fact that they included a Soviet spy ring is notable, but their contribution to understanding the workings of networks does not seem very significant.

But some of the networks he discusses are clearly relevant. One is Alcoholics Anonymous. This group offered "a twelve-step path back to sobriety," Ferguson writes, "but its real strength lay in the therapeutic network effects of regular meetings at which experiences of addiction were confessed and shared." Ferguson attributes its success to its "quasi-religious and wholly unpolitical character" and wonders whether, had it somehow been linked to communism, J. Edgar Hoover would have placed it under surveillance.

Ferguson is enthusiastic about ­criticizing hierarchical rule, or at least its authoritarian excesses, but he is also quick to finger the dark side of networks bent on hatred, plunder, violence, and, in our day, cyber-terrorism (think of ISIS or the WannaCry virus). At one point he writes: "The lesson of history is that trusting in networks to run the world is a recipe for anarchy: at best, power ends up in the hands of the Illuminati, but more likely it ends up in the hands of the Jacobins." Ferguson, a disciple of Edmund Burke, is no admirer of ­Jacobins.

While it's not difficult to heuristically appreciate the archetypes of hierarchy and network, the "square" and the "tower" are inherently blunt tools for the analysis of social and political movements and organizations. There are hierarchies within networks, networks within hierarchies, and a vast range of commingled life forms that defy simple taxonomy. Henry Kissinger, Ferguson's favorite networker, was of course the foreign policy director of the United States government hierarchy.

But there is a conflict in Ferguson's own thinking about hierarchies and networks as well. "The near-autarkic, commanding and controlling states that emerged from the Depression, the Second World War, and the early Cold War exist today, if at all, only as pale shadows of their former selves. The bureaucracies and party machines that ran them are defunct or in decay. The administrative state is their final incarnation," he writes. "Will the new networks liberate us from the shackles of the administrative state, as the revolutionary networks of the 16th, 17th, and 18th centuries freed our ancestors from the shackles of spiritual and temporal hierarchy? Or will the established hierarchies of our time succeed more quickly than their imperial predecessors in co-opting the networks, and enlist them in their ancient vice of waging war?"

The fact that today's most celebrated cyber-networks (Facebook, Google, Twitter, Baidu, Alibaba, Tencent) are centrally controlled by hierarchies suggests that networkers' power to control, influence, or undermine those hierarchies may be limited.

Ferguson concludes that "unless one wishes to reap one revolutionary whirlwind after another," the alternative to a world run by networks, some of them villainous, is a "pentarchy of the great powers"—like the 19th century alliance among Germany, France, Italy, Spain, and Great Britain—in which the members "recognize their common interest in resisting the spread of jihadism, criminality, and cyber-vandalism." But where is the assurance that these Platonic guardians, these hierarchs, will act in society's best interest rather than their own? The multitude of available networks today plays an important role in checking and even bringing down culpable hierarchies, he thinks. If the hierarchies start banding together, what then?

Ferguson recognizes this dilemma, but he doesn't have a reassuringly workable answer. Nonetheless, his book raising the question is well worth the reading.