At its core, this book addresses the question raised by Asimov (his protagonist Hari Seldon, a scientist of Psychohistory from the Foundation Trilogy): Is a science of history possible? Can we design a theory for the collapse of mighty empires that would be no worse than, say, our understanding of why earthquakes happen? Again, here's a nice succinct summary of the book from the author (tl;dr):

The very stability and internal peace that strong empires impose contain within it the seeds of chaos. Stability and internal peace bring prosperity; prosperity causes population increase. Demographic growth leads to overpopulation; overpopulation causes lower wages, higher land rents, and falling per-capita incomes for the commoners. At first, low wages and high rents bring unparalleled wealth to the upper classes, but as their numbers and appetites grow, they too begin to suffer from falling incomes. Declining standards of life breed discontent and strife. The elites turn to the state for employment and additional income, and drive up its expenditures at the same time that the tax revenues decline because of the impoverished state of the population. When the state’s finances collapse, it loses control of the army and police. Freed from all restraints, strife among the upper classes escalates into civil war, and the discontent among the lower classes explodes into popular rebellions. The collapse of order brings in its wake the four horsemen of apocalypse—famine, war, pestilence, and death. Population declines, and wages increase, while rents decrease. As incomes of commoners recover, the fortunes of the upper classes hit the bottom. Economic distress of the elites and lack of effective government feed the continuing internecine wars. But civil wars thin the ranks of the elites. Some die in factional fighting, others succumb to feuds with neighbors, and many just give up on trying to maintain their noble status and quietly slip into the ranks of commoners. Intra-elite competition subsides, allowing order to be restored. Stability and internal peace bring prosperity, and another secular cycle begins. “So peace brings warre and warre brings peace."

Cliodynamics: science of history

Turchin coins a new term for the science of history called Cliodynamics. It may be sciencey in spirit, but isn't really quantified, and appears to be quite far from even the rigor of a social science. Nonetheless, it's super interesting! Here are some patterns Turchin points to:

• New empires and nations are born at metaethnic frontiers, where us-versus-them mentality is strongest. This is in line with the worldview in Huntingdon's Clash of Civilizations.
• Successful empires grow under two conditions: 1. when their citizens have a high level of asabiya (aka Social Capital) and 2. when they are good at incorporating new members and treating them as equals (makes me think of the continuous expansion of "white people" in the US)
• Empires falter when asabiya goes into decline (Robert Putnam's Bowling Alone is all about how it's declining in the US).
• Social Capital isn't about morality. For example, it's not the case that social power must come from democracy. It can come from tribalism or elsewhere. To be successful, even an oppressor group needs to be socially cohesive.
• Asabiya can also increase as a response to new invaders, for example "Prior to the conquest of the sub-Saharan Africa by western powers in the 19th century, Africans had no sense of shared identity. But shared experience of first colonization, then decolonization, and now the tendency of the rest of the world to lump them together."
• Civil war tends to recur during the disintegrative phase with a period of 40 to 60 years. Turchin calls such dynamics the fathers-and-sons cycles. The survivors of the civil war and their children had direct experience of conflict, so are reluctant to allow the hostilities to escalate again, but the grandchildren of the civil warriors did not experience its horrors first hand.
• Turchin presents a much more nuanced view of a cyclical view of history than The Fourth Turning, "The fathers-and-sons cycles are nested within secular cycles, which in turn are nested within asabiya cycles." Ultimately this nesting leads to unpredictable timelines, and in general chaos theory means that dynamics of real human societies cannot be accurately predicted far in the future because of the nature of chaos, free will, and natural disasters. "Hari Seldon was wrong."

Asabiya and inequality

A big cause of the decline in asabiya is economic inequality, which tends to increase under normal circumstances ("Matthew principle") and largely because of population growth. Beyond just economics, "the degree of solidarity felt between the commons and aristocracy, is one of the most important characteristics explaining its success at empire building."

Wealth inequality tends to be reduced as population density decreases, either through deaths or increase in territory:

• Death: "Black Death had a beneficial effect on the survivors. The drop of population set in motion the Malthusian machinery, but now working in reverse."
• Increase in territory: happens naturally at the frontiers of an empire as it is growing. this was true in Russia when it was conquering east into the Siberian steppes, and in USA as the Americans expanded to the west. The frontier provides rewards for risk taking, and more upward mobility.

Confirming my suspicions from an explorable exploration I made a while back: "The only way to stop this process constantly breeding inequality is by either abolishing private property altogether or by abolishing the right to inherit it. A milder form of keeping inequality in check is a steeply progressive tax on inheritance. In other words, some sort of redistributive scheme could be used."

At one point the author digresses into the economics of agrarian land distribution, and describes a series of simulations he ran. I think doing something like this as an explorable explanation would be super fun. Imagine a visual treatment of a country split up by multiple families, and how that split changes through the generations. Here are some variants to try:

1. Equal distribution of land to heirs but unequal numbers of children per family.
2. Primogeniture, where oldest son gets all land.
3. First son gets half of the inheritance, but the remainder is divided equally among others.
4. Wealthier men tend to choose wealthier brides.
5. Some people are just more effective than others.

Cooperation versus individualism

Turchin details how cooperation was once understood to be the main basis of human society, but this view fell out of favor in modernity. The rise of economics and the popularity of “rational-choice theory” postulated that people behave in entirely self-interested manner. This is supported by many leading thinkers:

• Hume (1711-76) wrote, “Political writers established it as a maxim, that, in contriving any system of government ... every man ought to be supposed to be a knave and to have no other end, in all his actions, than his private interest.”
• Mandeville (1670-1713) wrote in The Fable of the Bees: Private Vices, Publick Benefits: “Thus every Part was full of Vice, yet the whole Mass a Paradise.” This does sound familiar. Wasn’t it the motto of the exuberant 1980s and 1990s—“greed is good”?
• Smith is best known is his “invisible hand” argument.

The problem: "When the group size becomes large enough, cooperation among rational agents unravels as free-loading becomes rampant. The collective-action problem strikes again." An interesting study shows that people across most societies naturally fall into 3 categories when playing repeated games: 25% fully selfish, 25% fully selfless, 50% tit for tat. some exceptions: Israelis are more selfish (lowball offers), while Lamerla are incredibly selfless. There is a continuum between individualism and cooperation, and we've probably over corrected towards the former.

Historical trends

Turchin looks at a wide variety of examples to make his points, and I learned a lot trying to keep track of various indigenous proto-nations. Many of his insights span across a long period of time, unite many seemingly unrelated civilizational conflicts:

• One ancient source of metaethnic strife is farmers vs. shepherd-nomads: "as exemplified by the biblical parable about the conflict between Cain with his fields and Abel with his flocks. (Because the early Hebrews were herders, naturally the evil guy in the story was Cain.) In eastern Europe, from the tenth century on, the cultural chasm was further deepened by the tendency of the settled cultivators to adopt Christianity opposed by the inclination of the nomads to Islam." This continued in America where the Europeans were farmers and the indians were nomads.
• A failure mode for Asabiya is social conservatism. In pre-unified Russia, each prince tried to resist the Tatar-Mongol hordes on his own, and all lost in a typical example of the tragedy of the commons. In south Italy, primacy of family unit caused people to distrust their neighbour, preventing large scale social collaboration and economic prosperity.
• Religion/race is a huge unifying force and common in meta-ethnic conflict. For example Christians vs. Pagans in the Russian conquest of Siberia, Christians vs. Muslims during the Crusades, in Iberia and in the new world. This was also true for early Romans, who were bound together by religion.
• Recurring thought: perhaps we'll need aliens to bring all of humanity together: "Thus, in the old Europe, although the Irish hated the English, and the French fought against the Germans, in the New World all these people cooperated with each other and fought together against the Indians".
• Wealth and power physics analogy: "Distribution of landed wealth within the society usually correlates very well with the distribution of political power, because wealth and power are akin to potential and kinetic kinds of energy in physics. Wealth, or rather income derived from it, is readily converted into power by buying influence or hiring retainers. Vice versa, political power brings with it the ability to acquire land, thus storing power for future use."
• Interesting that slavery has a negative impact on Asabiya in general. Putnam points to a “striking correlation between low social capital at the end of the twentieth century and slavery in the first half of the nineteenth century."
• Asabiya applies also to corporations: "Asabiya is as important in large multinational corporations today as it was in Virginia in 1700 or North Africa in the fourteenth century.", and "Ironically enough, although externally corporations brutally compete in the free market, their internal workings rely not on market forces, but on group solidarity! This is one of the best-kept secrets in the economic sciences. Just as you cannot construct a viable society, so you cannot put together a viable company from knaves alone."

Rome and Italy

• The Roman notion of Limes encompasses some combination of border, wall, and road. I haven't thought about these concepts as being so interconnected.
• There was no ethnic link between the Byzantines and the Romans: "Just designating themselves as “the Romans,” however, is not a sufficient reason to equate this later people with the Romans. For example, there is a modern country whose citizens still call themselves “the Romans”: Romania. In general, an appropriation of an old and glorious ethnonym (“a name of a nation”) is a common thing in history"
• Interesting parallels between Livy's account of "rampant luxury and conspicuous consumption of his own times, the first century B.C., with the simpler, less-materialistic mores of their ancestors" and the way people romanticize America today.
• Early Rome was incredibly cohesive because of huge vertical integration, and virtues that discouraged individualism: gravity, constancy, piety, faith: "When 50,000 Romans, a staggering one fifth of Rome’s total manpower, perished in the battle of Cannae, as mentioned previously, the senate lost almost one third of its membership. This suggests that the senatorial aristocracy was more likely to be killed in wars than the average citizen. Add this to the peculiarly Roman practice of “devotion,” which was always performed by a member of noble lineage, and it is easy to conclude that generally Roman aristocrats led the commoners in battle, and were the first to die."
• Unlike Athens and Sparta, Rome did a good job of integrating its subjects into the empire.

Muslim world

• Islam as an attractive religion for those that recently experienced chaos: "This quality of Islam continues to aid its spread even today. Ten years after experiencing the horror of civil war and genocide, many Rwandans are turning to Islam. During the decade since 1995, the number of mosques in Rwanda doubled to 500". All Muslims are unified in the umma, which let Muhammad unify multiple tribes into a meta-tribe.
• Through this lens of us vs. them, good explanation for Austria-Hungary's failures: they weren't sufficiently united, and had a lot of internal conflict. Part of what kept the empire alive for so long was the 3 century long struggle against the Ottoman empire.
• On middle east, pretty sad projections: "Two centuries passed from the First Crusade, which arrived in the Holy Land in 1099, to the rise of Saladin’s Ayyubid dynasty in 1174. The Crusaders were expelled from their last stronghold of Acre in 1291." and then "occupation of Egypt by the British troops in 1882. The establishment of Israel in 1948 merely elevated it to new heights, and the second Iraq war increased the pressure to what might be an unbearable pitch for the Arabs. It is possible that the world changed so much from the days of Ibn Khaldun that his law of asabiya does not operate any longer. But is it wise to bet on it?"

Europe

• Southern Italy has been a disaster for 1500 years: "Peninsular Italy, including Sicily, remained an asabiya black hole from the collapse of the Roman Empire to this very day." The north has done much better, but still no large public italian corporations (Fiat is family owned.) Also, they have never been an empire. Italy was the only European state that was defeated by an African country (Ethiopia) in the nineteenth-century scramble for colonies. More on this in Putnam's book Making Democracy Work: Civic Traditions in Modern Italy.
• Interesting recurring metaethnic frontier: Romans vs Barbarians in early 1st millennium, and Frankish Christians vs. Norman/Viking pagans in early 2nd millennium. Also recurring alliances a milennium later: "The first members of the European Union were, and the most enthusiastic proponents of the European Union are, France, Germany, the countries of Benelux, and Italy—almost precisely the regions that were part of the Carolingian Empire."
• Germany had huge asabiya until WW2, but the shock of defeat and anti-Nazi propaganda discredited this identity. Is the same thing happening now in the US, as a result of several failed wars? Vietnam, Afganistan, Iraq?
• One common myth: that France’s troubles were brought by the persistent conflict with the English, known as the Hundred Years’ War (1338-1453). First, the dates 1338 and 1453 are completely arbitrary. almost every generation of the French and the English fought against each other during their “Thousand Year War” between 1066 and 1815.
• Overproduction of elites comes from education. This happened at times of crisis in the past: "At the University of Paris, it took eight years to earn a Doctorate degree in the thirteenth century (five years to obtain a Bachelor degree, then three more to achieve the Doctorate). In the fourteenth century, it took 16 years to earn a Doctorate. The cost of education increased much faster than inflation in sixteenth-century France. Enrollments in Oxford and Cambridge peaked just before the Great Revolution, and then declined during the eighteenth century."

Random learnings

• Siberia is named after the khanate of Sibir.
• The connection of паган (pagan) and pagans, which lost its original religious meaning and now just means “bad” or “evil.”
• in Arabic khalifa means “successor”.
• Jacobins & Jacobites are completely different and unrelated groups.
• Fascinating origins of tribal names: "In fact, the very name Suebi basically means “us” (“those belonging to our group”). Incidentally, the names of such modern nations as the Swedes and the Swiss have precisely the same origin. The name of the later Alamanni also expressed the same idea, but with a different means. Alamanni means “the (true, real) people,” clearly a variation on the “us” versus “them” theme.
• In France, Normandy is named after the Norse, and Brittany is named after Britain. Nice to make that connection, completely obvious in retrospect. Also it's bizarre to be personally named after a 10th century peoples (eg. Norman, Brittany or Frank).

Okay. I think I've distilled most of what I found valuable in the book (a lot). Let me complain just a bit. Firstly, there are way too many small ethnic groups for me to keep track of. Secondly, what's up with the formatting in the Kindle version? Lastly, I found that the book was not super well structured, jumping around conceptually, chronologically, and spatially, and going over the same ground multiple times. That all said, I'll be reading more Turchin in the future.