# Expected utility formalism

The expected utility formalism combines a probability distribution relating actions to their probable consequences, with a utility function over consequences of actions, in order to assign expected utilities to actions. A key issue is the form and derivation of the probability distribution relating actions to consequences, usually held to be a counterfactual probability distribution.

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• Expected utility agent

If you’re not some kind of expected utility agent, you’re going in circles.

• Expected utility

Scoring actions based on the average score of their probable consequences.

• Utility function

The only coherent way of wanting things is to assign consistent relative scores to outcomes.

• Coherent decisions imply consistent utilities

Why do we all use the ‘expected utility’ formalism? Because any behavior that can’t be viewed from that perspective, must be qualitatively self-defeating (in various mathy ways).

• Coherence theorems

A ‘coherence theorem’ shows that something bad happens to an agent if its decisions can’t be viewed as ‘coherent’ in some sense. E.g., an inconsistent preference ordering leads to going in circles.

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