Youness Ayaita

A variety of probabilistic measures have been proposed in the literature to explicate the concept of (incremental) _confirmation_. These have mostly been defended on the grounds of _a priori_ intuitions sharpened against stylized test cases. Yet the debate has not converged on a single measure, nor has it provided a principled underpinning for measure pluralism. We take a new direction, informed by the ecological rationality program, with both conceptual and methodological implications. Conceptually, if measures of confirmation are understood as (idealized) cognitive tools in ecologically rational inquiry, pluralism is no longer a bug but a feature: different measures are adapted to different epistemic tasks and environments. Methodologically, if we specify the epistemic task as _tracking the truth_, we may deploy the technique of _symbolic optimization_ to search for confirmation measures that optimally track the truth in simulated environments. Thereby we identify and study a new family of two high-performing measures of confirmation, which combine building blocks of previously known measures in novel ways.

Probabilism—the doctrine that ideally rational degrees of belief conform to the calculus of probabilities—is habitually defended by citing Dutch-book and accuracy-dominance arguments. Yet these arguments rely on premises that are not plausibly necessary truths. I argue that the premises in question can be understood as fixing a convention. Relaxing these premises leads to alternative calculi which—under permissive though not universal assumptions—are intertranslatable with the probability calculus. This applies to Dutch-book and accuracy-dominance arguments alike; a mathematical correspondence is shown to hold between them.