The Foundations of Normal and Abnormal Psychology/Part 1/X
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.