What makes a good prophecy?

11th January, 2024

A couple of years ago, taking questions on stage in front of a live audience, I was asked to do my duty as an economist and make an economic forecast. But the questioner had a demanding benchmark for what made a good prediction, informing me that the previous keynote speaker at this conference had been a prominent scientist, who warned of a deadly global pandemic. That was in the autumn of 2019. Would my forecast be as good?

I parried the question with two questions of my own: my interlocutor would never hear a more consequential forecast than what he was told in 2019, but had he done anything differently? I knew the answer was no. Why, then, was he so interested in hearing another prediction?

My non-answer was weaselly, yes. But the exchange points to a problem: producers of forecasts frequently give people warnings they ignore, and unless consumers of forecasts are honest with themselves about what they plan to use them for, their demand for a glimpse of the future seems fatuous. Or, to quote George Eliot, “Among all forms of mistake, prophecy is the most gratuitous.”

A reliable forecast can be an invaluable guide to action. Weather forecasts are an example. A prediction that it will rain tomorrow is less certain than a prediction that the sun will rise, but as an aid to planning our day they fall into the same category.

But my questioner wasn’t asking for a weather forecast or anything like it. He wanted me to spin an interesting story about an uncertain future, much as the scientist had spun an interesting story. (His story came true, but let’s not be too awestruck by that.) There are many such stories: about the dangers of artificial intelligence, or the possibility of a Chinese invasion of Taiwan. They are often useless, not because they are wrong (although they often are) but because we have no idea what to do with them.

Tolstoy was quipping about this problem in regards to the war of 1812 when, 50 years later, he wrote War and Peace: “Nothing was ready for the war which everyone expected.” (Dominic Cummings, special adviser to Boris Johnson as the pandemic arrived, quoted these lines in his recent witness statement to the UK’s Covid-19 inquiry.)

To pick a case from the 20th century, the US Naval War College undertook a war gaming exercise in 1932, which made plain the risk that US military bases might be bombed in an aerial attack originating from across the Pacific. As Steven Johnson describes in his 2018 book Farsighted, America’s naval strategists had been given a glimpse of the risk of catastrophe at Pearl Harbor. But they did not respond; instead they hoped for the best.

It is easy to see why some forecasters liken themselves to Cassandra, the Trojan princess cursed with the ability to see the future — and to be ignored. If we are to avoid Cassandra’s fate, there are steps we can take to make our prophecies useful. First, they must be clear and vivid. Cassandra’s warnings were vivid but cryptic: “Keep the bull away from the heifer! She’s caught him in her dress, her engine, on her black horn, striking.”

With hindsight, that was a premonition that King Agamemnon was about to be murdered by his wife, Clytemnestra. But only with hindsight. Better, says Jane McGonigal in her recent book Imaginable, is to visualise specific scenes from a future life. (This practice, sometimes called “episodic future thinking”, is essentially mental time-travel.) A warning in 2019 about a pandemic would have felt more real if it had encouraged people to picture themselves in that pandemic-affected future, each day starting with a Joe Wicks workout and the fortunate few having a cupboard full of face masks, toilet paper and spaghetti.

I can’t promise that episodic future thinking really will unlock the future. I doubt we could have imagined April 2020 from the perspective of October 2019, even if we were certain a pandemic was coming. But any attempt to imagine the future in concrete, everyday terms can be surprisingly insightful.

Second — and this might seem paradoxical — a good prophecy must recognise that the future is unknowable. War and Peace had a line about this, too: “What science can there be in a matter in which, as in every practical matter, nothing can be determined and everything depends on innumerable conditions, the significance of which becomes manifest at a particular moment, and no one can tell when that moment will come?”

That is why I would rather have two vivid, plausible, contradictory scenarios to consider than one. A single forecast offers false certainty, assuming we believe it at all. But two compelling explorations of mutually exclusive futures? Now we are starting to move away from the sterile question “what will happen?” and towards the fertile question “what would we do if it did?”

Third, forecasts need to be crafted with a particular audience in mind. Ideally, that audience would actively participate in the process rather than passively consume the result. War games, role-playing exercises and scenario workshops can all help. If a forecast doesn’t address the concerns and the blind spots of its audience, it will be ignored.

For a forecast to be useful, it is neither necessary nor sufficient that it be accurate. That might seem a bizarre claim, but we only know whether a forecast was accurate when it is too late. In advance, what we can hope for from our prophets is that they open our eyes to different plausible futures, motivate us to anticipate threats and opportunities and remind us that, in the end, the future cannot be known. It can only be imagined.

Written for and first published in the Financial Times on 8 December 2023.

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