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 a vera causa, an agent that is observable in nature. But, as we have already shown, the transmission hypothesis lacks this essential requirement. Its agent, disembodied consciousness, is not a vera causa, nor can it ever be drawn into the circle of experience. A good hypothesis must be framed with a view of becoming a possible fact, but this hypothesis from its very nature disclaims this possibility, since its agent is in a region that lies outside our world of experience.
For this very last reason, namely, for speculating in things extra-mundane, the hypothesis may also be charged with committing transgressions in metaphysics. Such a hypothesis is the more metaphysical as the phenomena under consideration are dealt with as if they were entities.
Furthermore, the hypothesis only seemingly holds to the empirical law that consciousness is a function of the brain. For if consciousness is in a separate world all the psychic phenomena are in existence from all eternity, ready made, the phenomena of consciousness have really nothing to do with the brain, inasmuch as they exist from all eternity, in a region outside and totally independent of the brain. Thus the hypothesis by its very character, even if the matter be regarded from a purely logical standpoint undermines the proposition which it undertook to explain, and as such can hardly be considered as valid.
Finally, it may be urged, that the invocation of an extra-mundane world helps matters little, as it does not show the modus operandi of the interdependence of mental and physical phenomena, inasmuch as the rising or falling of a physical threshold does not in the least explain or show how a stream of consciousness is made possible to vary in volume and intensity. Without explaining the proposition that mental processes vary as physical processes, the transmission hypothesis only assumes an additional world of disembodied consciousness and thus gratuitously multiplies entities.
X The Metaphysical Hypothesis of Parallelism
The Spinozistic doctrine of parallelism claims that the mental and physical orders run parallel to each other, taking its stand on purely metaphysical grounds, namely, on the existence of one substance with an infinite number of attributes, all expressing the nature of this substance. Two of these attributes, being mind and matter which in an infinite number of parallel running modes or phenomena express the nature of this one substance. A modification of the unitary substance regarded under the attribute of mind is a mental mode or phenomenon. The same regarded under the attribute of matter or extension is a material mode or physical phenomenon. Mental and physical phenomena are both manifestations of one unitary substance. There is no need for me to point out that this double aspect of one unitary substance belongs to metaphysical dogmatism, of substantialism, and as such cannot possibly be admitted into the province of psychology as a natural science.
The voluntaristic school does not acknowledge a strict parallelism in the sense of a double aspect of the same unknowable or of two infinite attributes of the eternal nature of the same substance, but it does teach a psycho- physiological parallelism, grounding it on the double as pert, subjective and objective, of one "unitary" experience. This differs but little from the substantialistic dogmatism. Instead of one unitary substance the voluntarist substitutes a no less metaphysical category of "unitary experience."
Another metaphysical view of the new associationist or sensationalist school grounds parallelism on epistemological and metaphysical grounds. Psycho-physiological parallelism is partly a matter of pure definition, partly a matter of philosophical considerations. This school defines a psychic object as one belonging to a single subject, one individual only, while a physical object is one belonging to many subjects. Now, reasons this school, if psychology is to be a science at all, it must surely be of such a nature as to be communicated to other subjects, that is, it must become common property, and since by definition, only a physical object is an object of many and is communicable, hence a psychic object to become communicable must be expressed in physical terms.
This excursion into the region of metaphysics and epistemology of the otherwise matter of fact and common sense school is
