All Interesting Behavior Is Overdetermined

This is an essay about individual rationality technique. It's intended to show that "All interesting behavior is overdetermined" is, under a specific meaning of "overdetermined" that is stronger than just "multicausal", a valuable heuristic for generative understanding and the avoidance of error. Scott Alexander's 2018 essay The Omnigenic Model As Metaphor for Life is a clear statement of what has become general rationalist doctrine on multicausality. Scott observed that behavioral genetics was difficult because complex human traits involved far more interacting causes than workers expected. He draws this methodological lesson: “We should go from trying to discover ‘the’ cause, to trying to find out which factors we need to create the best polycausal model.” He applies the same reasoning to depression, intelligence, comma, and other complex psychological phenomena. He explicitly warns against looking for one or ten causes when there might be dozens or hundreds. Scott is, however, talking mainly about contributory causation, when an effect is produced by an accumulation of causes; in his type example, there are probably twenty thousand genes which contribute to intelligence, but no one "intelligence gene". This is not quite the same as overdetermination, which describes a situation in which a complex behavior could be explained with any one of multiple causes, each one in itself sufficient. When we find a sufficient explanation, or a sufficiently good collection of contributory explanations like Scott's 20,000 genes, there's a strong tendency to think that we can stop there. The rest of this essay is about why we shouldn't. I first came to understand the importance of overdetermination when I was studying primate ethology. There is a 1987 paper by Hausfater and Takacs, Structure and Function of Hindquarter Presentations in Yellow Baboons (Papia cynocephalus). It examines a striking feature of baboon social behavior: individuals turn their hindquarters toward anothe