Reason (argument)

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).

Debates concern what reasons are and how they work. Some hold that normative reasons are facts (or true propositions) rather than mere beliefs; others link them more closely to an agent's perspective. Reasons are said to play both a deontic role (helping to determine what one ought, may, or must do) and a deliberative role (serving as appropriate inputs to sound deliberation and, when taken up, becoming motivating reasons). Further questions include whether acting rightly must be done for the right reasons to have moral worth, and how normative and motivating reasons are related when guidance is difficult (for example, in surprise-party or akratic cases).

The literature also distinguishes epistemic reasons (which count in favor of believing a proposition) from practical reasons (which count in favor of actions or attitudes), and asks whether there is a unified treatment of both—e.g., by understanding reasons as a kind of evidence. Disputes about the source of practical reasons are framed as internalism versus externalism: internalists tie a person's reasons to their actual or idealized motivational set (sometimes in broadly Humean terms), while externalists allow that there can be reasons independent of an agent's present motivations. A separate contrast between agent-neutral and agent-relative reasons concerns whether the content of a reason makes essential reference to the agent (as with special obligations to one's child) or not (as with impartial welfare considerations).

Because agents often face multiple, context-sensitive considerations, contemporary work analyzes how reasons are weighed, defeated, or enabled. Proposals address holism about reasons, pairwise and contrastive frameworks for permissibility, possible incommensurability or parity among options, and distinctions between justifying and requiring strengths. Related topics include exclusionary (higher-order) reasons that bar acting for certain first-order reasons, and questions about aggregating overlapping considerations. These issues connect the concept of a reason to broader discussions in ethics, rational choice, epistemology, and the theory of argument.