Helenus and the Reverse Prophecies
Taleb uses Helenus’s ability to predict the past as an analogy for gaps in historical knowledge. Reconstructing an outcome requires evidence that may be missing, even when a retrospective story sounds convincing.
THE IDEA
Helenus and the Reverse Prophecies
If you are in the business of being a seer, describing the future to other less-privileged mortals, you are judged on the merits of your predictions.
Helenus, in The Iliad, was a different kind of seer. The son of Priam and Hecuba, he was the cleverest man in the Trojan army. It was he who, under torture, told the Achaeans how they would capture Troy (apparently he didn’t predict that he himself would be captured). But this is not what distinguished him. Helenus, unlike other seers, was able to predict the past with great precision—without having been given any details of it. He predicted backward.
Our problem is not just that we do not know the future, we do not know much of the past either. We badly need someone like Helenus if we are to know history.
When to use it
When writing a historical account, explicitly acknowledge gaps in the record and consider multiple interpretations.
In organizational learning, challenge post-hoc rationalizations by listing alternative plausible narratives.
When evaluating personal past decisions, list what information was unavailable at the time to avoid overconfident hindsight.
In policy analysis, use counterfactual thinking to explore what could have happened differently, rather than assuming the outcome was determined.
FROM THEORY TO EVERYDAY LIFE
In practice
The historian's certainty
A historian might confidently explain the causes of World War I as a chain of clear events, but in reality, many documents and perspectives are missing. They are essentially 'predicting the past' with incomplete data, much like Helenus.
Business post-mortems
After a successful product launch, a team may attribute the success to their brilliant strategy, ignoring the role of luck and missing data about unforeseen market conditions. They create a reverse prophecy that makes the outcome seem inevitable.
A MOMENT TO REFLECT
Put it to work.
Recall a major historical event you think you understand well. What specific details might you be missing that could change your interpretation?
Think of a time you or your team conducted a post-project analysis. How might you have been guilty of 'predicting the past'?
How can you systematically test your assumptions about past events to reduce reverse prophecy bias?
CONTINUE THE CONVERSATION
Source texts
- The Black Swan The Impact of the Highly Improbable With a new section On Robustness and Fragility (Nassim Nicholas Taleb)