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 the result of good intention of being thorough-going, hence, this metaphysical definition of mental and physical phenomena of the "one" and the "many."
Another argument adduced by the same school seems to be somewhat more sound. Physical facts it is alleged have a necessary causal connection, while psychic facts are only connected by association, which is not one of necessity. An idea a is sometimes followed by idea b and sometimes by idea c and so on. There is no invariable connection in psychic life, such as is to be found in physical facts. The soundness of this argument, however, is rather questionable. For it may be contended that no fastening bonds are ever observed in physical phenomena, the only thing observed is a relation of sequence of antecedent and consequent, and in case of causation an invariable sequence of a definite antecedent and definite consequent. Now psychic facts also manifest relations of sequence, we observe antecedents followed by consequents.
The argument that an idea is sometimes followed by one and sometimes by another idea showing the absence of invariable sequence is, if looked at closer, of a rather dubious character. An idea a or idea b is only objectively the same, by having the same object, but the thought, mental stream, or moment consciousness that possess that idea may not be the same, but it is just this mental stream, the moment-consciousness that determines the content of the succeeding idea. The thought of a is different according to the difference of the mental stream or moment consciousness. It is one of the psychologist's fallacies to consider that if the object is the same then the thought that possesses the object must also be the same. Now ideas of the same a are totally different in different mental streams, Just as two different minds regarding the same object have absolutely different psychic states. It is therefore clear that an idea a may be sometimes followed by b and sometimes by another idea. An idea a followed by b is altogether different from idea a followed by c. It is only the recurrence of the same mental stream or moment consciousness that would give the same sequence. This is clearly observed in hypnoidic states where the same moment consciousness recurs, the same sensations, ideas, feelings, and actions follow in invariable succession.
XI The Unitary Experience of Voluntarism
In the course of our discussion, we had again and again to refer to the data and postulates of psychology. It would be well to give now a short review of them so as to bring them clearly before the mind of the reader. The fact that the postulates are not kept clearly in view leads one to commit many a fallacy.
Psychology assumes the validity of unanalyzed criteria of reality taken as valid by common sense. The verification of illusions, hallucinations, and delusions is finally based on the dictum of common sense. The work of science may after all be nothing but an illusion, an hallucination, or a delusion of consciousness. What keeps up the scientist in his work is his firm belief that mankind believe in it, and that when other people are put under the same conditions they will verify his experiences.
Science assumes the postulates on which all experience of common sense is based. Science furnishes our knowledge of the external world, but science is essentially not self-conscious, and it cannot therefore on its own grounds answer the question as to the validity of its knowledge. Is there something independent in that externally perceived object, the house, for instance, or is the psychic account all there is to it? This is a problem not to be answered on psychological grounds. Knowledge, its possibility, its nature, and its general aspect must be taken for granted. Psychological knowledge, general for all subjects must be assumed, as well as general knowledge of the objective world. The psychologist, like other scientists, must assume that his experiences are so conditioned, that though they may be unique, still if others were to be put under the same conditions and confronted with the same external realities, they would pass through similar experiences. In short, psychology assumes the validity of its knowledge, its general validity for all knowing subjects, also knowledge of an externally