Our purpose in this chapter is to introduce briefly some of the main topics with which we shall be concerned throughout the rest of the book. These topics fall into two major categories: (1) metaphysical and ontological problems concerning the intentionality of acts of consciousness and the status of the objects toward which intentional phenomena are directed; and (2) logical and semantic problems concerning the behavior of linguistic expressions in intensional contexts, specifically, in sentences attributing intentional phenomena to persons. Here we shall concentrate on describing in as theory-neutral a way as we can the characteristics of mental phenomena that constitute their intentionality and the characteristics of act-sentences that constitute their intensionality, and we shall suggest ways in which intentionality and intensionality are related. It will be the task of subsequent chapters to develop a theoretical framework within which these characteristics of acts and act-sentences can be systematically explained and understood.