In philosophy and argumentation, a reason is a consideration that counts in favor of a conclusion, action, attitude or fact, or that explains why something is so. Reasons typically answer a why? question and are often introduced by expressions such as because, since, as, in virtue of, or in order to. They are central to accounts of practical reason, epistemic justification, moral evaluation, and everyday explanation, and they figure prominently in law and deliberative discourse.
Philosophers commonly distinguish three roles for reasons. Normative (or justifying) reasons are considerations that count in favor of responding one way rather than another (e.g., that it is raining is a reason to take an umbrella). Motivating reasons are the considerations in light of which an agent acts—what the agent treats as counting in favor at the time, whether or not it in fact does. Explanatory reasons cite what explains an event or action; when agents are involved, these often refer to psychological states (for example, that someone believed they were late explains why they ran).