In recent years, philosophers have been much concerned with questions about the contents or meanings of the sensation concepts that we employ in everyday life. They have presented and defended a wide variety of positions. At one end of the spectrum is the view that our sensation concepts acquire their contents from internal ostensive definitions, and that these concepts are therefore purely phenomenological, in the sense that the question of whether a given concept applies to a given sensation depends entirely on the immediate phenomenological nature of the sensation. At the other end of the spectrum we find the view that our concepts of sensations are similar in content to theoretical concepts such as the concept of gravity and the concept of electric charge. According to this second view, the contents of our sensation concepts derive from the roles that the concepts play in our commonsense theory of mental activity. This view denies that the question of whether a concept applies to a given sensation has anything to do with the immediate phenomenological nature of the sensation. To determine whether the concept applies to a sensation, the view maintains, it is necessary and sufficient to consider the causal role that the sensation plays in the internal economy of the being in whom it occurs. If the sensation bears the right causal and counterfactual relations to other things (namely, to external stimuli, to behavior, and to other internal states), it falls under the concept.