This is a grisly and depressing tome if I have ever read one, though hopelessness and despair are common features of the human experience. They are cornerstones in our history, and we ignore history’s tragedies to our own peril. Inspired by Thomas Piketty’s Capital in the Twenty‐​First Century (2013), Walter Scheidel draws together a vast array of quantitative and narrative evidence for his central thesis that

A classicist, historian, and demographer all in one, Scheidel integrates a variety of world historical evidence into a convincing, if depressing, portrait of wealth equalization over time and across space. Most world histories are plagued with problems that only a regional specialist might recognize, but Scheidel does not allow himself to stray from the subject at hand and his narrative plays a structural, supportive role for the real star: huge amounts of data on inequality.

I am an intellectual, social, and political historian interested primarily in ideas, individuals, institutions, and the interactions between each. I am not a quantitative historian and am in no way qualified to speak on the validity of Scheidel’s argument in this regard. My goal, therefore, is to take his case as given and proceed to distinguish the implications for libertarians and libertarianism if indeed significant leveling of wealth has occurred only as the result of widespread death and destruction.

The volume begins with a broad discussion of the argument, methodology, and “A Brief History of Inequality,” from the primordial use of brute force to the modern exercise of international finance capitalism. At no point does the author endorse either equality or inequality. Rather, he argues that the concentration of wealth (measured primarily by Gini coefficients — “the extent to which the distribution of income or material assets deviates from perfect equality”) has been a fundamental fact of human existence, essentially, forever. The fruits of inequality include the ultimate foes in libertarian thought, the state and all its attendant extractive parts. The egalitarian harvest, however, is a bloody and detestable mess. Scheidel maintains a careful and measured distance from his subject, able to recognize the very real social and historical problems associated with both concentration and compression. Both processes included horrifying levels of violence, and neither is truly preferable. With a word of caution to the modern devotees of “equality at all costs,” Scheidel writes,

Scheidel leads us backward in time from the present day through the democidal 20th century, the beginnings of imperialism and capitalism, the medieval and ancient eras, to the origins of the human species. Spatially, we are pulled from the United States to Soviet Russia, from industrial Europe to Qing China, from the Han dynasty frontier to the Roman Empire, from plague‐​infested Constantinople to plague‐​infested Lima. He argues that the hunter‐​gatherer way of life demanded fewer and simpler possessions, but sedentary agriculture encouraged the accumulation of property and heritable wealth. Those who accumulated the most wealth tended to acquire political and even spiritual authority as well. Over time, divisions between the power of some and the helplessness of others calcified into socio‐​political class hierarchies, conceptions of political authority, justice, and general ideas about how the world simply or naturally was. Material inequality played a critical role in the development of states, and states in turn ensured the continued existence of particular concentrations of wealth. This process has taken place only under conditions of extended peace and relative prosperity, however, leading Scheidel to argue that “the absence of major violent ruptures has been a vital precondition of high inequality” (p. 62).

This is certainly not to say that the Roman and Han Chinese empires were peaceful or peace‐​generating institutions. Rather, Scheidel treats political units as mere bodies or vehicles for the exploitation of labor and the expropriation of resources. The Roman and Han states existed to serve the purposes of those societies’ elites — namely, protection for the concentrations of wealth and power these individuals managed to amass or inherit. The results in civilizations across the world have been largely the same: inequality is steadily built up and its attendant problems exacerbated until the requisite level of “despotic intervention” reaches a socially or technologically intolerable point. In such collapse‐​ready situations, one or more of Scheidel’s “Four Horsemen” run amok, razing cities and civilizations alike.

After the Roman collapse, the Plague of Justinian, and centuries of low‐​level warfare, medieval Europe suffered the worst devastation in its history during the 14th and 15th centuries. The Black Death wiped away at least a third of the population and leveled wealth concentration more than any single event before the Second World War. High wages encouraged migration to urban centers, and by the early 1400s Gini coefficients in Italian, German, and Dutch cities reached from the 0.7s to the 0.9s. As Scheidel notes, “High wealth inequality of at least 0.75 was a standard feature in the­ major cities of late medieval and early modern Western Europe” (p.­ 93). From the 15th to the early 20th century, inequality steadily increased worldwide. Despite periodic local or regional moments of leveling, the general trend points to a centuries‐​long process through which the wealthy and powerful amassed more and­ more over time. Elites funneled their windfalls into capital investment, colonial corporatist ventures, and the professionalized fusion of modern statecraft and business interests. While plagues certainly operate as powerful temporary levelers, they spare capital wealth and the productive capacity of the land. Our next “Horseman” is not so discriminating.

War destroys land, labor, and capital alike. The more modern the conflict, the more total its destructive capacity. Before the era of mass mobilization warfare, conflict between armies accounted for only small and discrete moments of leveling, if not a further concentration of wealth. In the modern era — since roughly the Napoleonic Wars — mass armies and weapons capable of destroying entire nations have dramatically expanded the leveling capabilities of the warrior Horseman. The strongest example of “total war” leveling is 20th century Japan. In 1938, near the height of imperial Japan’s power, the wealthiest 1 percent of the population claimed a fifth of total income and Japanese Gini coefficients may have ranged from 0.45 to 0.65. During the decade and a half of Japanese warfare, the top 1 percent’s share of income fell to a meager 6.4 percent. The most elite of elite estate values declined more than 90 percent. Almost all of the wealth concentrated among Japan’s wealthiest and most powerful was claimed by the war effort, physically destroyed in the fighting, or redistributed by the postwar regime. “Total war ended in total defeat” and near‐​total leveling of wealth.

Together, the world wars created a “Great Compression” of wealth inequality. Throughout the world, inequality trends roughly corresponded with the more dramatic Japanese example and for largely the same reasons. Those countries most deeply touched by the war generally experienced the greatest amounts of leveling, and, if Scheidel and Piketty are to be believed, inequality is slowly creeping back up to prewar levels. Importantly, though, these events were not conscious attempts at leveling wealth. Rather, they were the catastrophic results of long‐​standing foreign and domestic policies and deep cultural conflict.

Purposeful and violent leveling through revolution has been a powerful correlative to the unintended consequences of modern mass warfare. The leveling effects of violence are far sharper if the poor kill the rich and redistribute physical wealth rather than destroying it outright. As it happens, though, the revolution rarely stops with the 1 percent, and violence can quickly consume a society. In Russia, China, and a host of other countries, revolutionary regimes not only murdered private wealth holders in numbers rarely seen throughout history, but they also attempted to abolish inequality as a matter of law. The horrifying examples of Soviet and Maoist democide illustrate the devastating hazards of pursuing equality at the costs of humanity.

Our final Horseman is that which brings state failures and systems collapses. While this is the least well‐​documented phenomenon covered in the book, it is among the more interesting and probably has been the most potent leveler. In these cases, entire social structures could be wiped clean. In the case of Tang China, warlords purged virtually the entire ruling aristocracy. As the Western Roman Empire fell, its social‐​political organization and even basic productive technologies like the pottery wheel disappeared. The most dramatic example is the Late Bronze Age collapse, perhaps prompted by invasions, natural disasters, and the Hittite Empire’s fall (c. 1200 BC). In Mycenae, Mayan Central America, and ancient Harappa, systems collapse entailed the liquidation of wealthy elites and most concentrated capital. Scheidel argues that, despite the relative lack of modern examples or complete data, “Ozymandian collapse may well have been the single most potent and reliable leveler in all of history” (p. 279). Much rarer than bouts of disease or warfare, civilization‐​ending failures are nearly always more complete levelers — so complete, in fact, they often take any data with them into the dustbin of history. To make matters worse, Scheidel investigates supposedly peaceful alternatives to violent leveling and dismisses each in turn. Nothing but violence, or activities associated with violence (like land reform or emancipation), have had an appreciable negative effect on inequality.

What are we, then, to take from this unfortunate yet well‐​researched volume? Those of a hopeful cast of mind may be uncomfortable accepting Scheidel’s claims, but those claims have a firm basis in liberal social and historical theories. The liberal theory of history posits that any social use of individual power necessarily divides the population into antagonistic factions — those who positively embrace said use of power and benefit from its use, and those whose liberties are constrained. When the powerful accumulate and exercise enough power in foolish or tyrannical ways, the libertarian interests of exploited individuals will no longer bear it. The resultant clash between the powerful and the exploited produces change over time and constitutes the stuff of history. This is the theory given down to us by Guizot, Acton, Croce, and innumerable others; and, though it demands some qualification to account for nonsocial levelers like plagues and pandemics, it is perfectly consonant with Scheidel’s presentation of war, revolution, state failure, systems collapse, and their attendant consequences for inequality. Still more important, though, the liberal theory of history offers potential solutions to the “Great Leveler Problem” that inequality has been built on violence and only mass violence has ever seriously reduced inequality.

Scheidel largely discounts the possibility of peaceful reform, but perhaps what we need is a nonviolent systems collapse or an individualist revolution. If we can manage to combine the strongest horsemen with the ideological opposite of coercion, perhaps we can both reduce inequality and do so nonviolently. Rather than a true collapse, this might look more like a systems replacement. Instead of absolute leveling through nuclear annihilation, we might achieve it through digital currency reform, the 3‑D printed domestic economy, an artificial intelligence explosion, space exploration, or the perfection of genetic manipulation. We might level inequality with any number of technological singularities or moral‐​cultural revolutions, but we should recognize that violence nearly always begets violence. In a world where our next mass conflict could be our last, no one should be willing to take the risk. As we lurch forward into an uncertain new era fraught with potential catastrophe, we should be mindful that power can never be trusted and its steady — but peaceful — ­dismantling might make the difference between survival and extinction.