lucid, but it does not mean that one can see a candle shining through it. The energy of mental phenomena is as much the energy of physical and physiological sciences as the idea of a brick is a brick itself and made up of clay.
Furthermore, were it possible that a physiological process should be converted into a mental process, the law of conservation of energy would have to be given up, and along with it the whole edifice of modern science would tumble to the ground. For according to the law of conservation of energy no physical energy can possibly be lost. One form of energy may pass into another, but the physical energy which is some form of motion, molar, molecular, atomic, ionic or electronic cannot be lost, that is, there must always be so much motion, no matter under what form it may appear. Now on the one hand, were it possible that a physiological process, which is nothing but a form of physical energy, could pass into a psychic state, which is no motion at all, we would really have a loss of energy. Were it on the other hand possible that a mental or psychic process should pass into a physiological process, we would have had new energy generated, energy that is not a transformation of some previous existing energy, or physical activity.
If mental and physiological processes were to stand to each other in relation of antecedent and consequent, in relation of cause and effect, we would have had with each beat of consciousness a new creation of physical energy and a loss of it with each cerebral process. This would be sufficient to undermine the basis of science, and .practically we might have had good hopes that in the near future our steam engines would be run by good intentions and windmills by aesthetic feelings.
Psychic and physiological series are no doubt intimately related, but their relation is not causal, they do not stand to each other in relation of invariable succession characteristic of cause and effect, but in that of co-existence. The two series of processes are concomitant, they run parallel to each other, but neither is the cause of the other. A change in the one means also a simultaneous, concomitant modification in the other. In other words, every psychic change must have its physiological concomitant, and vice versa, every physiological process may have its psychic accompaniment. This hypothesis of psycho-physical parallelism is at the basis of all modern psycho-physiological, neurological, and psycho-pathological investigation, inasmuch as it is taken for granted that for every manifested sensori-motor or ideo-motor "symptom" there must be present term for term some physiological process. Psychology takes the same view and accepts the same hypothesis; it does not trouble itself in the least with the philosophical problem as to whether the two series of phenomena, the mental and the physical, have behind them separate substances, or whether they are but two different aspects of the same thing. This belongs to metaphysics. The psycho-physiological theory like all other scientific hypotheses has nothing to do with metaphysical substrata, but deals only with facts and their relations.
XIII The Deductive Basis of the Positive Psychological Hypothesis
The concept of causality cannot be worked in psychology in the same way as it can be done in the physical science. The circle of physical processes is complete in itself. A physical process without ceasing to be physical can be traced endlessly in the past or future, all the links of the endless process must all be physical in their nature. For if we permit in the endless chain of links of the physical process any other but physical links to be interpolated, all the physical sciences must fall to the ground, since at any stage we may get hold of a process of which the antecedent link is not of a physical nature. In short, the postulate that forms the basis of physical science is that the antecedent and consequent of a physical process taken at any stage of the process are physical in their nature. This is the principle of continuity. The whole edifice of the physical sciences is based on this principle.
If we now turn to psychology, we find that it cannot be based on a postulate of similar character. Psychology cannot possibly work on the assumption that the processes it deals with can be traced endlessly in either direction, past, or future. Unlike the physical, the psychic process is finite and final,―it has a beginning and an end, it begins with a purpose, conscious, subconscious, or unconscious, and ends with an adjustment. The psychic process begins as a sensation, and its complete cycle runs its course as an idea and then ends in a volition to act. The stimulus marking the beginning of the psychic process and the act marking the end of the process are physical links of a continuous physical process, the links of which can be traced endlessly in physical terms. Taking the psychic process from the ontogenetic standpoint, we find again the same thing. If the psychic life of the individual is taken as a whole and traced backward, in the past, we arrive at some point, when the i stream of consciousness begins, and on following it forward, we finally arrive at a point where the stream of consciousness ends. If we view the question phylogenetically, we come once more to the same conclusion. In the history of biological evolution there was a time when psychic life began, and there will come a time when all psychic life will disappear from our globe. The principle of continuity, the warp and woof of physical science, cannot be worked in psychology, instead of it we can only discover a principle of finiteness and finality.
In a physical process any link taken at random must have a physical antecedent and consequent; not so is it in a psychic process, not each link of the series has its psychic antecedent and consequent, the first link has no antecedent and the last one has no consequent. The phenomena of sleep, of hypnosis, of amnesia, of unconsciousness, of syncope show that the psychic process may be cut short anywhere in its course, and may resume its flow from any given link or stage. The links that go to form the psychic process hang loosely, and any link may really be without an antecedent or without a consequent.
In many cases the seemingly lost antecedent can still be found in the subconscious, dissociated from the active stream of consciousness constituting for the time being the conscious personality or the self-consciousness of the subject, such for instance is the case in the many forms of functional psychopathic diseases and also in hypnosis. In other cases, such for instance, as unconsciousness of epilepsy, the stream of consciousness is interrupted and resumed only after a certain period of time, not even the subconscious can supply us the missing link. In normal sleep we meet once more with an interruption of the current of consciousness, and it is only under certain conditions, such as dreaming, that the subconscious can supply the missing states. Each psychic process is like the life process of a given individual, it has a definite beginning and a definite end; while a physical process has neither beginning nor end, and can be followed out endlessly in the direction of the line of antecedents or consequents. In other words while a physical process is infinite, a psychic process is finite.
Let P be a physical process and p represent a link in that process, then p1, p11, p111, etc., may be represented as its consequents, while p1, p2, p3, p4, etc., may be represented as its antecedents. P therefore may be represented by the following infinite series:
P= … … +p4+p3+p2+p1+(p)+p1+p11+p111+p1111 … …
The series is infinite in both directions, in direction of p, antecedents, and in the direction of p consequents.
Let S represent a psychic process, s a link in that process, s1 s11 s111 s1111 etc., its consequents s1, s2, s3, s4, etc., its antecedents, then the psychic process can be represented by the following series:
S= … … +s4+s3+s2+s1+(s) X s1+s11+s111+s1111+ … …
Now this series is finite, it begins at some link and ends with some link, neither the beginning nor the end is defined,―the series may begin at any link and end at any link. Since the process may begin anywhere in the series, there is really no necessary connection between the links of the series. In the physical process on the contrary, the series is infinite, and any link has a determinate necessarily gives preceding and succeeding link. In other words, while the links of the physical process are necessarily causally connected, the links of the psychic process have no causal