Sebastian Sanchez-Martinez
TU Dresden
According to recent work in epistemology, the main function of beliefs is the simplification of reasoning (SR for short). Beliefs are here understood as attitudes that, beyond an agent’s voluntary control, take the proposition that is their content as true. This is SR with respect to working with credences, understood as degreed attitudes that don’t dispose an agent in an equal way to treat a given proposition as true. For instance, while Fernanda’s belief in p exclude belief in not-p, Fernanda’s credence of 0.9 in p allow a 0.1 credence in not-p. Working with credences in reasoning often involve complex calculations, heavy use of memory and the application of rules that are not easy to follow. This observation, backed up by empirical work in computer science and cognitive psychology, makes SR necessary. The mechanism behind simplification is the ignoring of certain unlikely alternatives to p that don’t affect the agent’s final attitude, while saving her cognitive resources.
The resulting picture is a heuristic view of belief. In this picture, belief is a heuristic that automatically and defeasible allows Fernanda to treat p as true, while her total evidence supports forming a more degreed attitude. The problem: An agent’s total evidence warrants probabilistically coherent outcomes in reasoning, and ignoring unlikely alternatives includes a degree of probabilistic incoherence. The discouraging diagnosis is that beliefs are often probabilistically incoherent.
In this presentation I aim to show a strategy to solve the problem of probabilistic incoherence for SR. First, I show the difficulties faced by extant solutions to the problem. Second, I identify a premise in the argument for the incoherence of SR in which probabilistic coherence is a necessary condition for the rationality of an agent’s attitude. Finally, I propose to disambiguate “rational” in the premise, thus allowing for a sense in which rational beliefs can be the result of SR.
Chair: Morgan Adou
Time: September 8th, 10:00-10:30
Location: SR 1.004
SOPhiA 2026 