survival of the survivors

A thought, while writing the last post. Thinking about international politics invariably involves a lot of rational-choice stuff, or rational-choice at one remove. Although this may not make sense in a platonic game-theory way, how do so-and-so’s interests, preferences, and meta-knowledge of their own situation have to differ from yours to make it work? They’ve been arguing about this over at Crooked Timber for some time.

It struck me, anyway, that this is a lot like the notion of “fitness” for biologists, which is famously problematic. Everyone’s heard of “survival of the fittest”, but what is “fit”? Clearly, it means something like “able to survive”. So we’re talking about the survival of the survivors, which is not very useful. Survivors survive. No shit, Sherlock. Similarly, how do we know that some actor did something on the basis of a rational judgment? Because if it didn’t fit their preferences they wouldn’t have done it!

There’s another issue here, too. The statement that the survivors survive is tautologous, but it’s not a stupid statement. Reflect on the survival of survivors, and you will actually learn something about evolution – that it is driven by chance, that it is without aim, that it is not teleological or value-laden. Ug’s genes were conserved because the cave didn’t collapse on him. We are full of hacks and errors that continue to exist not so much because they helped our ancestors survive, but because at some crisis in the past they were irrelevant and therefore not selected out. Survival itself is often a matter of chance.

We look around and see rational choices, but we’re afflicted by enormous survivorship bias – however irrational your choices, if they didn’t lead to total failure, they will be justifiable in hindsight as rational on some terms. Now, the biologists eventually got rid of the survival of the fittest, and biology as a science gained immensely from unpacking the idea. Rational choice has something else in common with the survival of the fittest. Herbert Spencer probably didn’t mean the phrase as an exact statement of theory, but as an elegant popularisation. And rational choice is a bit like that, too – the very simplicity of the idea explains why it survives.

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