A clairvoyant is a mythical character who can foretell the future, usually for a fee, provided he is given a well-defined question (one that passes the clarity test). The concept of the clairvoyant is useful in decision analysis for ensuring clarity of thought, particularly when assessing information in the face of uncertainty. Being able to meaningfully call on the clairvoyant is subject to important restrictions about the nature of free will.

See also: Context, Value of Information and Wizard.