 Perhaps she has some practical decision that involves not only hens but also the presence of frightening dogs in the yard. She might wish to feed the hens but will only do so if there is no dog in the yard. If she were ignorant of whether there is a dog in the yard, the number of scenarios she must consider in her deliberations grows to four. Clearly, one needs to consider epistemic alternatives when one does not have complete information concerning the situations that are relevant to one’s decisions. As we shall see below, possible worlds semantics has provided a useful framework for understanding the manner in which agents can reason about epistemic alternatives.