ABSTRACT
The elicitation of a good set of possibilities is a necessary step for taking reasonable actions or making decisions. However, it is not a sufficient step. Even when the set of possibilities is well defined, exhaustive, and exclusive, the listing of possibilities does not, in itself, indicate which decision or action is best. For the decision as to how to deploy the police searching for the missing child (see Chapter 3), the listing of the possible whereabouts of the child is not enough. The decision depends on our confidence in each one of the possibilities (as well as on other considerations). Thus, an additional necessary step in any decision we make is to define our confidence or degree of belief in any one of the elicited possibilities. In Chapter 1 we saw that the degree of belief is a personal, subjective feeling; its external manifestation can give an outsider an idea about it. In the present chapter, we will inquire into the ways we usually express degree of belief, and we will discuss how it actually should be done.
