Although the parallelism theory is correct as far as it goes, there are two empirical facts connected with the relations between mind and body of which it contains no suggestion. The first of these is the fact that, while the physical series is continuous, the mental one is interrupted and incomplete, only a minute fraction of all the processes that go on in the physical world being accompanied by consciousness. It appears as though physical facts could exist without mental, but not mental facts without physical; as though, in other words, physical facts constituted the basis upon which mental facts rest. This appearance is strengthened by the second fact referred to, namely, that any interference with the normal course of the cerebral processes is at once followed by alterations or even by total suppression of consciousness; as where lesions of circumscribed cortical areas abolish certain classes of memories without affecting others. It is the desire to offer some explanation for these two empirical facts which leads Dr. Münsterberg to his doctrine of the dependence of mind upon body.
From the point of view of empirical investigation there is little to be said against this doctrine. Nerve-physiologists, experimental psychologists, and scientific alienists employ it constantly as a sort of working hypothesis, and their right to employ it is beyond question. At the same time they cannot be too often reminded that it is only a brief, compendious phrase to express the empirical facts respecting the relations between body and mind — the fact of parallelism, the fact that the mental series is interrupted, and the fact that interference with the physical series is accompanied by alterations of the mental — not a theory aiming to explain these facts.
When the doctrine is propounded, as it is by Dr. Münsterberg, for the purpose of explaining the empirical facts, it becomes an unmistakable piece of metaphysics; for it is impossible to explain the empirical relations of mind and body without transcending the limits of experience. What is more, it is a piece of very questionable metaphysics; for the doctrine that mental events depend for their existence, not upon the unknown reality that appears to us under the form of a material world, but upon these material appearances themselves, is indistinguishable from philosophical materialism, and open to all the objections that lie against that doctrine.
While abandonment of the common-sense theory must influence one's whole psychological attitude, evidently no theory will be more affected than that of the will. In volition we have as nowhere else the feeling of our own activity; and the question arises, how this feeling can be reconciled with a theory which regards all mental states as the passive concomitants of events in the brain. Dr. Münsterberg has given an an
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