Withhold by default: a difference between epistemic and practical rationality

Abstract In practical rationality, if two reasons for alternative actions are tied, then either action is *permissible*. In epistemic rationality, we get the Epistemic Ties Datum: if the reasons for belief and disbelief are tied, then withholding judgment is *required*. I argue that this difference is explained by a difference in default biases. Practical rationality is biased toward permissibility. An action is permissible unless the specific features of the situation (e.g., the costs and benefits that apply) make it prohibited. In contrast, epistemic rationality is biased toward withholding judgment. Withholding judgment is required unless the specific features of the situation (e.g., the evidence) makes belief or disbelief permissible. This difference explains the Epistemic Ties Datum. When the reasons for belief and disbelief are equally weighty, they cancel each other out. But then the only remaining reason is the default reason, or default bias, to withhold judgment. Since it is the only remaining reason, it requires us to withhold judgment.