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-Decision theory solves the extremely hard problem of telling you what you should do if you have a perfect model of the world and a utility function telling you how good any particular world-state is. The most common decision theories are evidential decision theory and causal decision theory; various [[accursed decision theories]] exist but are not in wide use.
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+Decision theory solves the extremely hard problem of telling you what you should do if you have a perfect model of the world and a utility function telling you how good any particular world-state is. The most common decision theories are evidential decision theory and causal decision theory; various [[accursed decision theories]] exist but are not in wide use.
+
+== Evidential decision theory
+
+EDT says, informally, that you should take whatever action has the highest expected utility (i.e. the sum of utility for each outcome weighted by the probability of that outcome conditional on you taking the action).
+
+== Causal decision theory
+
+Informally, CDT says that you should take whatever action //causes// the highest expected utility, i.e. the conditional probability is replaced with a counterfactual (there is some debate about how to operationalize this, but roughly speaking, it's the probability if you replaced the action you took with another one).
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