That this view of conscious behavior should involve an extensive reinterpretation of familiar facts is altogether natural and inevitable. If consciousness is a form of control, the question, for example, what is "in" consciousness and what is not must be interpreted with reference to this function of control. In a sense we perceive many things to which we are not paying attention, such as the light in the room or the familiar chairs and bookcases. These are perceived "marginally," as we say, in the sense that the presence of these objects affects the total adjustment of the moment in such a way that the experience _would_ become a clue to these objects if they were withdrawn. And similarly we may speak of marginal sensations of strain or movement, to indicate possible clues to certain bodily activities which are factors in the process. These marginal perceptions or images are not actual existences, but are symbols and nothing more. The significance of these symbols is that they point to certain conditions by which the experiences in question are determined. Thus the question whether a given experience involves certain "sensations" is just a question whether certain bodily or extra-bodily conditions are involved in the experience. If this reference to conditions is ignored and experience is explained in terms of sensory material that blends and fuses and otherwise disposes itself, the explanation is no longer science but sleight-of-hand. Psychology has no proper concern with such mythical constituents of consciousness; its business is with things as related to conduct, which is to say that psychology is a science of behavior. II According to the standpoint set forth in the preceding discussion, the key to a consistent and fruitful interpretation of consciousness and psychology lies in behavior. If we turn now to the psychology of introspection, which has been dominant so many years, we find a standpoint and mode of procedure which, on the surface at least, is of a radically different kind. It behooves us, therefore, to consider this standpoint in some detail in order to justify the attempt to reinterpret and "evaluate" it in the light of our own doctrine.