Principle of Maximum Expected Utility

utility-theory

Definition

Principle of Maximum Expected Utility

The Principle of Maximum Expected Utility states that a rational agent, given evidence , should choose the action that maximises its expected utility :

Concretely, with the expected utility

given outcomes and utility function , the principle says: pick the action whose probability-weighted average outcome utility is highest.

Reading

The principle is the decision rule that turns a rational agent’s goal — “do the right thing” — into a concrete selection criterion over the action set . It is the bridge between expected utility as a numerical evaluation of a single action and rationality as behaviour: rationality asks for the best action, and “best” is defined here as maximum expected utility.

Not Omniscience

Not omniscience

Evidence may be incomplete, so can be wrong in hindsight; the principle only commits the agent to the best action given what it knows.

This mirrors the same limit on rationality: rational omniscient, because the agent’s percepts may lack relevant information.

Vacuous Without a Utility Function

Vacuous without a utility function

If is unspecified, every action trivially maximises . The principle prescribes behaviour only once fixes what counts as desirable.

Without , the maximisation is a comparison of unlabelled numbers; with , the same comparison becomes a meaningful preference ordering over actions.