Dr. Münsterberg's answer to this question is contained in the query whether the activities usually ascribed to consciousness cannot be equally well interpreted as mere passive changes taking place in the conscious content. On this view it would be the conscious content itself which now expands, now contracts, now entirely disappears; the elements of which flow together or apart; and which, by means of a definite complex of sensations and mental images, produces the impression of an arranging, comparing, selecting activity.
The contrast between this and the ordinary view will be apparent if we reproduce Dr. Münsterberg's account of attention. The ordinary view supposes that in attention the sensation or idea attended to suffers no change, but that consciousness itself increases in distinctness; while the accompanying sensation of strain is explained as an immediate consciousness of the mental activity involved. Dr. Münsterberg, as we know, explains the latter sensation as of muscular origin, and as due to tensions partly in the muscles of accommodation of the sense-organs involved, partly in the muscles which serve to fixate the head and to regulate respiration. The action of these muscles, particularly the more exact adjustment of the muscles of accommodation, has the effect of increasing the sharpness and distinctness of the individual sensations and ideas that make up the conscious content; and this result is at the same time helped on by the exclusion of inhibitory ideas and the reinforcement of favoring ones. Attention thus involves no activity of consciousness itself, but consists solely in changes taking place in the conscious content according to the laws of association, and is therefore perfectly intelligible on the parallelism theory.
But if consciousness has no power to interfere with the movement of our ideas, this is at least not true of the Ego, the most characteristic of all mental facts, which manifestly exerts a predominating influence in our mental life. What is to be made of the Ego upon the parallelism theory?
The word Ego, as commonly employed, designates two entirely distinct mental facts, which we may call the subject Ego and the empirical Ego. The subject Ego is identical with that abstraction of consciousness which may be distinguished in thought from the sensational and ideal content, but which cannot exist separately from it. The Ego in this sense possesses no physical substratum. Psychologically, it is the mere passive spectator of its momentary content, which it is powerless to act upon or alter in any way; while epistemologically, it is the absolute precondition of knowledge and of existence. The empirical Ego, on the other hand, which is the Ego we think of when we think of ourselves, the Ego which governs the course of our ideas, the Ego which acts and suffers, is a part, and for each human being the most significant part, of
