The Groom and the Addict: Does Committing to Difficult Endeavours Require Belief Against the Evidence?

Evidentialism holds that a person’s beliefs should align with their evidence. Berislav Marušić denies this. Consider when a person promises or resolves to complete a difficult endeavour, such as staying married or quitting smoking forever. Given the difficulty of the endeavour, there is a significant chance they will fail. In such cases, Marušić argues, the normative demands of ‘sincerity’ require the person to believe they will succeed—that is, they should believe they will fulfil their promise or resolution—despite their evidence indicating a significant chance of failure. Thus, Marušić argues, people should form contra-evidential beliefs in such cases. I defend Evidentialism against Marušić’s challenge. I argue that requirements to be sincere when making promises and resolutions cannot create requirements to form beliefs against the evidence. Instead, sincerity restricts what we can promise and resolve to do. We must only promise and resolve to do things that our evidence suggests that (given that we committed) we will do. By highlight costs of contra-evidential promises, resolutions, and beliefs, I argue that restricting ourselves to evidence-aligned beliefs better supports our aims, agency, and relationships. Finally, I propose redesigning marriage vows to better align with the available evidence and human values.