Swans on trains, accidentally and chaotically

Behavioral New World

April 1, 2026

Swans on trains, accidentally and chaotically

The phrase “black swan” first appeared in a poem by the Roman writer Juvenal sometime between 60 and 130 CE. It was popularized by Nassim Nicholas Taleb in his book The Black Swan: The Impact of the Highly Improbable. It refers to the occurrence of an unlikely, unexpected event.

Where does the modern usage of the phrase come from? For many years, Europeans had seen only white swans and thus assumed that all swans were white. But in 1697, a Dutch explorer encountered black swans in Australia. Quite unexpected! A more complete discussion of black swans can be found here.

In Taleb’s telling, a black swan event is not only largely unpredictable—because of its highly improbable nature—but also because of its extreme impact. Examples might include the 2008 financial crisis and the Covid epidemic.

An individual-specific version of a black swan is the “sliding doors effect,” the notion that a seemingly small event can significantly change the course of a person’s life. This is the premise of the film “Sliding Doors” (1998) in which we see two life paths for the main character. In one scenario, she narrowly beats the sliding doors and gets on the train. In the other scenario, the doors close before she can get on. Her life is quite different in the two scenarios.

Whether or not she gets on the train is an extreme event for her, if not for the world at large. I suspect that each of us has felt, at least at times, that our lives could have changed significantly but for a seemingly small event. “Because I missed that plane, I met my future spouse,” that sort of thing.

The physicist Murray Gell-Mann has suggested a similar, if not identical, phenomenon which he calls “frozen accidents.”[1] He states, “Each of us human beings…is the product of an enormously long sequence of accidents, any of which could have turned out differently.” Getting on the train (or not) is one such ‘accident.’

Frozen accidents can also be important at the macro level and thus change history. Consider the assassination of Archduke Franz Ferdinand, widely regarded as the spark that started World War I. Ferdinand’s car took a wrong turn during his visit to Sarajevo, the Bosnian capital where he was killed (details here).

Of course, we don’t know what would have happened if his car had not made the wrong turn, but it is easy to imagine a distinctly different history unfolding (but not necessarily no war). The “accident” of Ferdinand’s assassination is said to be “frozen” because it cannot be rewritten or undone.

Black swans, sliding doors, and frozen accidents are reminiscent of chaos theory. I make no claim to a full understanding of chaos theory, but you may have heard the expression, “A butterfly flaps its wings in Asia and creates a storm on the other side of the world” (there are many variations of this quote). I think this sentence, often used to describe chaos theory, captures the essence of black swans, sliding door events, and frozen accidents.

How is an understanding of BSSDFAC (black swans, sliding doors, frozen accidents, and chaos—a perfectly unpronounceable acronym) useful to us? Can we really do anything about unpredictable events? I offer some thoughts here and would love to hear your thoughts. Click on “Comment” below. You are also welcome to suggest how “BSSDFAC” might be pronounced.

First, an understanding of the chaotic path of history will prepare us to be less surprised when an unexpected event occurs. For example, we will be less likely to panic when the stock market drops rapidly (many investors sell at that point and rue the decision later). We haven’t predicted the market crash, but we’re not surprised by it.

Lisa Feldman Barrett, in her book Seven and a Half Lessons About the Brain, says, “It’s metabolically costly for a brain to deal with things that are hard to predict.” (p. 87) My take on that: We may be disinclined to contemplate unpredictability and consequently not take actions to mitigate the effects of BSSDFAC.

Second, we can work to build our resilience and mental flexibility. Emotional intelligence and mindfulness practices can also be helpful. A more detailed discussion of these techniques can be found here.

Third, in the financial arena, hedging instruments are available. For example, if your well-being depends on the price of oil (a relevant factor as I write this), you can hedge against price increases (or decreases).

Fourth, in the realm of personal finance, having a sufficient financial cushion can help us deal with negative surprises. The cushion reduces the anxiety we might feel in a time of greater-than-average economic uncertainty.

Finally, whether something goes viral or not is not predictable. This thought gives me hope that my newsletter might go viral. Could happen, you know. Share this post and maybe it will happen 😊

[1] For a lengthier explanation of frozen accidents, see this blog by Shane Parrish (link)