On Historical Parallels
We treat historical parallels as fodder for forecasting.
But it's generally more useful to think of them as fuel for generating meaning and ideas than predictions.
Foretelling the future is nearly impossible as it is. Adding historical analogies into the mix doesn't improve one's odds.
Consider the varieties of predictions based on similarities of America and ancient Rome.
At the founding, the comparisons generally had a positive color. Like the Roman republic, the American one would expand and revolutionize the world. The founders were aware of darker lessons from Roman history too: republics can be lost.
Today, the pronouncements are pessimistic, often predicting American decline because it shares a feature or two with the decline of Rome (or declines of Rome). Like the explanations of Rome's declines, the features are numerous. Candidates include increasing political violence, rise in deadlock factions, wealth inequality, imperial overstretch, loss of virtue, elite overproduction, and so on.
For example, here's a warning from Edward Watts referencing Appian's (questionable) account of election violence:
We need to condemn more clearly the insurrectionists' actions, to identify and punish all the perpetrators, and to remove the instigators from our public life. If we cannot do that, sedition, insurrection, and political violence threaten to become the most potent political tools in the America of the 2020s—just as they did in the Rome of the 90s B.C.
The point about the current moment is right, but it's not clear how much additional force it gets from referencing an election where one candidate murdered another. There's American political violence, and then there's Roman political violence – the first may be more expensive, but the latter was more deadly.
Consider another warning, given in 2007, by the former Comptroller General of the United States David Walker:
The Roman Republic fell for many reasons, but three reasons are worth remembering: declining moral values and political civility at home, an overconfident and overextended military in foreign lands, and fiscal irresponsibility by the central government. Sound familiar? In my view, it's time to learn from history and take steps to ensure the American Republic is the first to stand the test of time.
These comparisons don't have precise character.
One could sharpen them by constructing predictions. Good predictions have clear success criteria (like the dollar will fall to X by Y). Predicting "decline" is nearly unfalsifiable. Forecasting a rise in political violence is more precise. That's a measurable phenomenon, but ideally, one would say more. A prediction like: "Protests will cause an excess of $125 million of damage in 2021" is clear.
As predictions become more precise, the differences between historical periods become more salient. In America, we're predicting the political movements of a larger, richer, and more liberal body politic. America is the pinnacle of a WEIRD society: western, educated, industrialized, rich, and democratic. At times, Rome approached democracy but otherwise is radically different.
Vaclav Smil expresses the gulf of the differences in his helpful, Why America Is Not The New Rome:
Could an average American truly imagine a family life where one out of four newborns would not live to see the first birthday and average life expectancy would be only 20-25 years? Could a young American family contemplate with equanimity the prospect of a life whose physical quality would be inferior to that in the most desperate countries of today's sub-Saharan Africa? Could a young Roman woman, whose prospects of survival at age 20 were no better than to live to her late 40s, imagine a society where women lived on average past their eightieth birthday? And could an ordinary Roman family grasp the full reality of an economy whose annual average income would be 50, 80, or 100 times its own? Negative answers, in every case, are all too obvious.
So that's one problem with using ancient parallels to generate predictions.
Another: if historical analogies were useful tools for generating predictions, we'd expect people who were exceptionally good at forecasting to use them. That's not what we find. Phillip Tetlock and colleagues have cataloged the traits associated with superforecasting. In general, the thinking style is general rather than specific. It is "dragon-fly eyed," instead of seeing the world from the eyes of a specific theory, superforecasters view it through many. In answering the question, will this dictator hold power for an additional year? Superforecasters would often take an "outside view" by considering when dictators lose power instead of an "inside view" that looks at specific features of the situation. It turns out a rather simple rule is reasonably accurate at predicting the answer.
None of these cognitive traits or tools include reasoning through historical analogies. Of course, looking at the past is useful, but through gauging the base rates of events, not by pulling out parallels.
Historical resemblances may not be good for prediction, but that doesn't entail that they aren't valuable.
They add meaning. Looking back to the Gracchi brothers reminds us of broad lessons, like the dangers of populism, the ignorance of elitists, and the logic of escalating violence. One has to be careful to avoid letting stories contaminate one's picture of the present. But they may still serve a useful role. Comparing future successes with past successes make them greater – as if they're following in the same lineage. History is full of heroes and villains that provide aspirational goals and anti-goals – even when the accounts are myth.
The past is also useful for idea generation. Take this example from Razib Kahn:
The social cohesion of the Roman republic was breaking down. Faction began to dominate all of public life.
Into situation stepped Sulla. Sulla is not a contingent man. Sulla is a type. A reaction, usually a vain and futile attempt to hold the past together, and push it into the future, by brutal means. Sulla arises when social elites lose faith in the present, and attempt to recreate institutions from an idealized past.
What would Sulla look like today?
That's a question that admits a wide range of answers.
A related spin from Nick Partyka:
Can we see in the success and popularity of Bernie Sanders and Donald Trump alignments of political forces akin to those that marshaled behind Marius and Sulla respectively? If the Roosevelts are the American Gracchi, and Sanders and Trump are the Marius and Sulla, then Whither our American Ceasar? Is our American republic on a similarly downward trajectory as the Roman republic? Do we live in the age of a moribund republic?
I don't know the answers to these questions. I ask them because of the thought they provoke or inspire in the reader.
Return to the past for meaning and perspective, but beware the temptation to play Sibyl.