  This informal problem description can be recast, slightly more formally, in terms of three sorts of entities. First, there are outcomes—objects of non-instrumental preferences.  In the example, we might distinguish three outcomes: either I end up dry and unencumbered; I end up dry and encumbered by an unwieldy umbrella; or I end up wet. Second, there are states—things outside the decision-maker's control which influence the outcome of the decision. In the example, there are two states: either it is raining, or it is not.  Finally, there are acts—objects of the decision-maker's instrumental preferences, and in some sense, things that she can do. In the example, there are two acts: I may either bring the umbrella; or leave it at home. Expected utility theory provides a way of ranking the acts according to how choiceworthy they are: the higher the expected utility, the better it is to choose the act. (It is therefore best to choose the act with the highest expected utility—or one of them, in the event that several acts are tied.)