Although nothing (outside a formal system) can be completely defined, the clarity test allows the decision participants to determine whether such elements as variables, events, outcomes, and alternatives are sufficiently well defined to make the decision at hand.
In later teaching Howard more broadly defined the clairvoyant as a person with perfect knowledge of all events and measurable quantities, past present and future, but no judgment.
The concept of the clairvoyant is useful in decision analysis for ensuring clarity of thought, particularly when assessing uncertainty.
The wizard is another mythical character who can change the future, usually for a fee, provided he or she is given a well-defined request.
The concept of the wizard is useful for assessing deterministic preferences by eliminating the complexity added by uncertainty.