In this ambitious tome, ancient historian Walter Scheidel (Stanford Univ.) seeks to answer the famous question from Monty Python's Life of Brian:[1] "what has Rome ever done for us?" His provocative answer: fall and never return. He addresses a central problem of "Big History"—the causes and dynamics of the so-called "Great Divergence," the concatenation of explosive technological development and institutional reform since the eighteenth century. This phenomenon has dramatically if unevenly increased standards of living and life expectancies, first in Europe and North America, then across the globe. What brought about the Great Divergence and why specifically in Europe?

Scheidel accepts a common near-term explanation for the Great Divergence: competitive polycentrism in Europe. Interstate competition, though it provoked a succession of petty but often devastating wars, spurred technological and institutional innovation. The diversity within the system made it more likely that one state might produce institutions especially conducive to economic growth, overseas expansion, and technological development. Ultimately, Great Britain proved to be ground zero for the Great Divergence. Though this premise is widely accepted, Scheidel explores it in detail in his book's later chapters. His thesis is that this productive polycentrism would not have existed but for the fall of the Roman Empire. Europe is distinctive in having a single major empire in its history. But serial empire building was common elsewhere in the Old World, especially in China, where dynasties rose and fell on into the twentieth century.

The author first describes the unique formation of the Roman Empire: Rome began as a well situated but modest city-state in central Italy that was able by the late fourth century BC to dominate and absorb its immediate rivals. The city developed a historically exceptional system of mass mobilization from both its expanded citizen body and Italian subjects. In the absence of a peer rival able to match Italy's military demography, Rome conquered the Mediterranean and its continental environs. Scheidel is uninterested in the fall of the Roman Empire, noting that imperial collapse is an extremely common phenomenon. A far rarer problem is explaining why Europe was never again dominated by an expansive tributary empire.

State deformation in the post-Roman world was intense. Not only did political fragmentation (briefly reversed by the Carolingians) produce more and more smaller polities, but these were characterized by substantial internal fragmentation. Michael Mann's [2] four aspects of social power (military, ideological, economic, and political) had been united in the person of the Roman emperor. In the Medieval Latin West, however, these were now split between the Church (ideological), powerful landowners (economic), the knightly class (military), and weak kings (political). In China, the collapse of the Han Empire was also followed by a degree of state deformation, but after several centuries the recovery in state capacity was impressive: by the mid-eighth century, the Tang dynasty was registering 9 million households with 53 million people in its census and fielding armies with hundreds of thousands of soldiers (251).

Geographic factors explain divergent outcomes. China is more geographically unified than Western Europe, which is riven by mountains and sprawling coastlines. But Scheidel introduces a more compelling factor that links geography to military capacity: most Old World empires were formed close to the steppe, which provided horses, riders, and equestrian technical knowledge for empire builders. These were sometimes drawn, like the Mongols, from steppe peoples themselves. More often they emerged from adjacent settled polities well positioned to mobilize the resources of the plains.

Beyond the Hungarian plain, a small western outpost of the Eurasian steppe, pre-modern Western Europe was heavily forested, negating the counterfactual of a Mongol invasion of the Latin West. The Mongols had easily overrun the steppe portions of Europe, but their enormous mounted armies would have been frustrated by the lack of pasture, rugged terrain, and many stone castles, the latter a product of the region's political disunity. While medieval armies were also based on mounted knights, they were tiny and logistically constrained—a few thousand armored cavalry. Medieval battles were paltry by Roman or Chinese standards: the Battle of Hastings was fought between two armies with a combined strength of a mere ten thousand men. That most Eurasian, Iranian, and North African empires were based on mass cavalry forces made Rome's infantry-based empire all the more exceptional and irreplicable.

In Europe, fragmentation begat fragmentation, as the Catholic Church used its ideological power to undercut kings, who were forced to cede more and more land to win the loyalty of nobles and knights as communes and cities carved out local jurisdictions for themselves. But as weak and petty as Latin kingdoms appeared at the time, this proved to be a long-term advantage. The economic and military power of nobles, knights, and towns required kings to obtain consent through councils and assemblies. This, in turn, spurred the development of parliamentary forms. Within weak states, institutions arose with significant degrees of internal autonomy, most notably guilds and universities. While kings and the Church often tried to violently suppress dissent, their fundamental feebleness allowed a vigorous intellectual culture to develop, based on critique and disputation. Political disunity provided dissidents safe havens, most notably when insubordinate princes of the notoriously fractious Holy Roman Empire shielded Martin Luther.

In contrast, the reformed power of Chinese dynasties governed a more stable and even prosperous society, but one that lacked the dynamism of the small European kingdoms: imperial monarchy was unquestioned and largely unchecked. Confucian ideology stressed stability and status quo; elites devoted their intellectual efforts to memorizing classic texts, while mercantile interests were sidelined. The polycentrism of Europe meant that an entrepreneur like Columbus could pitch his plan to multiple courts till one agreed to his seemingly dubious scheme. While the famous treasure fleets of Heng Ze sailed familiar routes of the Indian Ocean, Chinese emperors, at the head of stable empires and inclined to maintenance over expansion, took little interest in Pacific exploration, even though a voyage to the coast of California was technically feasible.

Throughout, war was a critical driver towards modernity. Fragmented states in Europe faced a host of peer rivals, providing urgent incentive towards continuous military development. The result was brisk innovation in firearms, fortifications, battleships, and military tactics following the introduction of gunpowder in the fourteenth century. These developments not only gave European powers a dramatic edge in global conflict, but also increasingly demanded new administrative and institutional developments to support them logistically––the recursive process captured in Charles Tilly's famous aphorism: "war made the state, and the state made war."[3] In China however, imperial dynasties faced asymmetric warfare against steppe peoples along the frontier; hence they lacked incentive to constantly improve weapons, tactics, and institutions. Even though the Chinese had invented gunpowder and eventually guns, the development of Chinese firearms stagnated along frontiers lacking similarly equipped and organized opponents.

The benefits of life in a pre-modern empire like Rome or China included low taxes, political stability, relative peace, and even modest economic growth thanks to integration and specialization. As for personal well being and comforts, Hadrian's Rome or Ming China outpaced Germany during the Thirty Years War. The overarching costs of European polycentrism were indeed staggering: wars, genocides, slavery, and climate change. But the Panglossian argument ("all is for the best in this best of possible worlds") is well taken: the dynamic of European polycentrism explains why the boost in living standards first occurred in Europe. The fall of Rome had been a necessary, if distant, precondition.

The scope of Scheidel's erudition is breathtaking, engaging–often in considerable detail–with over two thousand years of European and Chinese history. The analysis will nonetheless be accessible to readers both outside and within academia. In short, Escape from Rome will serve as a landmark of Big History for decades to come.