The fact–value distinction is a fundamental epistemological distinction described between:

1. 'Statements of fact' ('positive' or 'descriptive statements'), based upon reason and physical observation, and which are examined via the empirical method.
2. 'Statements of value' ('normative' or 'prescriptive statements'), which encompass ethics and aesthetics, and are studied via axiology.

This barrier between 'fact' and 'value' implies it is impossible to derive ethical claims from factual arguments, or to defend the former using the latter.

The fact–value distinction is closely related to, and derived from, the is–ought problem in moral philosophy, characterized by David Hume. The terms are often used interchangeably, though philosophical discourse concerning the is–ought problem does not usually encompass aesthetics.