Some Mistakes Are Irreducibly Diachronic

The idea that people make mistakes in how they pursue their own best interests, and that we can identify and correct for these mistakes has been central to much recent work in behavioural economics, and the ‘nudge’ approach to public policy grounded in it. The focus in this literature has been on individual choices that are mistaken. Agreeing with, and building on the criticism that this literature has been too quick to identify individual choices as mistaken, I argue that it has also overlooked a kind of mistake that is potentially more significant: irreducibly diachronic mistakes, which occur when series of choices over time do not serve our interests well, even though no individual choice is mistaken independently of being part of the series. I argue for the claim that people make such mistakes, and reflect on its significance for welfare economics.