Epistemic luck

Epistemic luck is the way a belief can be true by accident, in a manner incompatible with its being knowledge. That knowledge excludes this kind of luck is one of the few points on which nearly all epistemologists agree; Unger made it the core of an analysis of knowledge, and Pritchard built an anti-luck epistemology around it.

Not all luck undermines knowledge. It may be lucky that I looked up just as a comet passed, but my belief that it passed is not thereby true by accident. Engel distinguished such evidential luck from veritic luck, and Pritchard isolated the kinds that matter: veritic luck, where it is a matter of luck that a belief is true given how it was formed, and reflective luck, where its truth is lucky from the believer’s reflective standpoint. Gettier cases involve veritic luck. Modal conditions such as safety and sensitivity are the main attempts to say what excluding it requires.

The concept matters for AI because frequency-reliable sources produce a distinctive kind of luck. A broken thermometer in a thermostatted room is correct every time it is read, for a stable and explicable reason. A belief formed by reading it is true, and not by a fluke in the ordinary sense. Yet its truth is accidental relative to the temperature, since nothing about the temperature explains what the thermometer displays. Grounded frequency reliability is non-accidental relative to the mechanism producing it while remaining accidental relative to the truth of the particular content.

That is the structure I find in language-model outputs, on the best current evidence about what governs their production. A user who comes to a true belief from such a source is not lucky in the gambler’s sense; the source is right far more often than chance. But if the truth of what it asserted played no role, through its own operation, in why it asserted it, her belief is true by a kind of luck that precludes testimonial knowledge, however impressive the aggregate record. What the record can give her is the warrant of an instrument she has validated.