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 necessity.
Since the two processes, the physical and the psychic are postulated to run parallel to each other, their coordination may be represented in the following series:
S … … +s3+s2+s1+ (s) + s1+s11+ … …
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P … … +p4+p3+p2+p1+(p)+p1+p11+p111+p1111+. … .
Each link of the psychic process has some link of the physical process as its concomitant.
s has p, s1―p1, s2―p2, s1―p1, s11―p11.
The psychic process not having its links causally connected, the causal necessity can only be followed along its concomitant physical or physiological series. Hence we can see why the physiological series is indispensable to the psychic series.
The finiteness of the psychic process makes it impossible to apply to it the principle of necessity. For while a physical process must necessarily have a physical antecedent and physical consequent, a psychic process and each link of it does not necessarily have an antecedent or consequent, it may begin and end at any link.
It is only by means of the physical or physiological series that the principles of continuity and necessary causal connection, the foundation of all objective science, can be worked in psychology. Without the help of the concomitant physiological series the investigator of the psychic process is, scientifically considered, completely helpless, since the psychic process has no objectively necessary causal interconnection.
The "Voluntaristic" school in attempting to make of psychology a science independent of all physiology is fundamentally wrong. Without the physiological series psychology has no cement to fasten its material with, it has no foundation to build on. Psychology can maintain itself in the work of objective natural sciences only on condition of its intimate interdependence with physiology. No psychology without physiology. The psycho-physiological hypothesis is both inductively and deductively the sine qua non of the science of psychology.
XIV Life and the Psychic Process
We have pointed out that the psychic process is essentially finite and final, can we find any other process that should be characterized by the same mark of finiteness and finality? We find an analogous process in life. The life process is one that has the aspect of finiteness. Ontogenetically, the life-process of an organism has its beginning in the fertilization or stimulation to life-activity of the ovum, and has its end in death. Phylogenetically, the life process runs a determinate course. There was a time when geological conditions did not permit the presence of life, and
