Before we dismiss the soul hypothesis, we may point out that it must be rejected on quite different grounds, it is at bottom unscientific, it is metaphysical, it goes into the ultimate nature of things, an investigation that does not fall within the province of science. The soul-hypothesis assumes the existence of an abiding unchangeable entity behind the veil of mental phenomena, an entity which in the flow and change the phenomena remains the same and is the really real, the ultimate nature of the facts of consciousness. This belongs to the ontological part of metaphysics, but should not be introduced into science. The reader will realize now, why the whole complicated "soul discussion" is taken up here. It is to emphasize the fact that psychology has nothing to do with substances, noumena, entities, and quiddities, that psychology has nothing to do with the "inner nature" of consciousness. Psychology, like all other sciences, describes, classifies, and investigates by means of observation and experimentation facts of consciousness and their relations, and endeavors to express these relations in general formulae or laws; all attempts to make of psychology more than this can only result in bad metaphysics.
The materialistic hypothesis is even worse metaphysics than is the spiritualistic one. It is a hypothesis which in spite of its evident absurdity is none the less in favor with some representatives of the medical profession. Matter and force, as Buchner puts it, give rise to, or produce consciousness, or as Cabanis and Moleschott express it "the brain produces thought as the liver secretes bile." This hypothesis is unscientific and metaphysical, because it attempts to penetrate into the inner nature of consciousness, and claims to have it resolved into "matter." It is bad metaphysics, because it takes its "matter" on trust, without any critical reflection. Moreover it is more crude and worse metaphysics than is the soul hypothesis, because it lacks even the recognition of the most elementary, psychological proposition, namely, the knowledge of fundamental difference between mental and material phenomena.
Turning now to the faculty-hypothesis, we find that it is nothing else than spiritualism under a somewhat different form. The faculty-hypothesis chops the mind into many different parts, termed faculties, one is for reading, another for speaking, another for remembering, another still for willing, and so on. Sometimes they are limited to a few, and sometimes they are multiplied to infinity. The faculty-hypothesis is a cheap edition of spiritualism, it is spiritualism many times over. Instead of one soul it has many of them. Spiritualism has but one difficulty and that is the soul which, like an omnipotent deity, presides in some mysterious way over mental and organic activities. The faculty-hypothesis has an infinite number of them, inasmuch as it multiplies the deity into an endless number of gods and spirits that take charge of different psychic and psychomotor departments.
One can see the reason of the faculty hypothesis. It originated with people who as a rule are inclined to accept uncritically words for realities. Thus, will, memory, words that are only collective terms for many different states of mind, names furnished by the language of unreflective common sense, are naively taken as indicating some substantial entities, or little spirits existing somewhere in the brain.
IX The Transmission Hypothesis
The transmission hypothesis advanced by James is a modification of the soul hypothesis. The transmission hypothesis postulates the existence of a physical world and of an independent universe of consciousness. Consciousness, however, cannot manifest itself in this sublunar world without the occurrence of definite physical changes. That level of physical changes which makes the manifestations of consciousness possible is termed the physical threshold. Now the ocean of consciousness pours forth its psychic waves into the material world with the rise and fall of the physical threshold. The threshold is to be pictured as a sort of flood gate regulating the volume and intensity of the transmitted current. The rising of the threshold diminishes the psychic stream, while the lowering of the threshold permits a greater volume of consciousness to pour over into our physical world.
The transmission hypothesis has certain advantages over the previous ones discussed by us. While this hypothesis postulates the independence of consciousness, it is also in accord with the scientific proposition now generally accepted, namely that mental life is somehow connected with or is a function of brain activity, only specifying that this function is one of transmission. It claims to fall in line with the threshold concept of psychophysics as worked out by Fechner, and further harrowed by the "new psychology" movement; moreover, it is comprehensive enough to embrace all the facts and speculations brought out by recent investigations in the domain of mental pathology.
The transmission hypothesis, however, has also disadvantages which are of such a grave nature as to make one hesitate to accept it. The transmission hypothesis from its very nature is unverifiable. For, if, by hypothesis, consciousness manifests itself in this sublunar world (the only one we know) only under physical conditions, how can we ever come to know and verify a postulated world of pure consciousness? Being outside the domain of our psychophysical world, the universe of disembodied consciousness cannot, by hypothesis, furnish us the means for its verification. In this sublunar world we can know of the existence of consciousness through its physical expressions, through its being embodied. How then, can we ever reach a universe of disembodied consciousness? But a hypothesis which from its very nature is not verifiable cannot possibly be accepted.
The transmission hypothesis is all the more unacceptable as the terms in which it is expressed are contradictory, and the analogy on which it is based is essentially illegitimate. Consciousness is supposed to be different in nature from the physical world and existing independently, the psychophysical threshold alone regulating the volume of the stream of consciousness to be poured over into the material world. The threshold then which is physical in character limits consciousness, but how can the two be limited by each other when they are totally different in nature? In assuming two different universes, we assert that the two cannot limit each other, but in examining again the concept of threshold we make a contradictory assertion that the two can and do limit each other.
The very analogy on which the concept of "transmission function" is based is illegitimate when applied to consciousness in its relation to the physical world. The concept of "transmission function" can only be applied to a case where the transmitter and the thing transmitted are of homogeneous terms, but not where the terms are essentially heterogeneous. A stream of liquid can be transmitted through a pipe, a beam of light through stained glass, or a Roentgen ray through soft or more or less rarified cellular tissue. Both the transmitter and the material transmitted are physical in their nature, but how can an idea or feeling such as our idea of eternity, or of infinity, or aesthetic, or moral sense be transmitted through a tube? How then can we apply the concept of transmission-function to consciousness and the physical world where the two are totally different in nature? The analogy is figurative and scientifically illegitimate.
The transmission hypothesis sins further by reason of its transcending the legitimate grounds of psychology. It assumes an independent world of consciousness which cannot be brought within the range of experience. Now even if it be granted that such a world does exist, it still falls outside the subject-matter of psychology. For psychology as we pointed out deals with facts of consciousness, with experiences and their relations. If it be objected that every hypothesis is extra-experiential, it may be pointed out that a hypothesis must be framed in terms that can be drawn within the circle of experience, it must use