There are two problems that every satisfactory theory of intentionality, or of mental reference, must be able to solve. The first is the problem of referring to non-existent objects. (We mentioned and briefly discussed this problem in our Introduction.) The second is that of referring to one and the same object in two (or more) different ways. For example, if you think of the evening star and I think of the morning star, we are both thinking of the same object, but under two different aspects.