and role played by the particular affected product in the total compound. Taking all this into consideration, I think that they are wrong who insist that the abnormal can be known only from the normal. We can realize now how superficial are those who tell us "we learn but little from the abnormal, for first of all comes the normal." We realize now how detrimental to scientific investigation such a contention is. As a matter of fact the progress of science is not from the normal to the abnormal, but the very reverse, from the abnormal to the normal; the normal is but an arbitrary temporary concept, modified, and determined by the abnormal or unusual.
The supreme importance of pathological research holds especially true in the case of psychology, where the phenomena and the conditions on which these depend are so highly complex and so intricate, appearing at the same time so simple and taken as a matter of course in ordinary life.
As we have pointed out in the investigation of mental life we may either change the psychic or objective content, or effect changes in the mental function itself. In the study of vision, for instance, we may effect changes in the conditions of external objects, leaving the eye itself undisturbed. We may keep the object at different distances and study its appearances, put the object in water and have it refracted at different angles; we may look at it through different prisms, colored glasses or contrast its color when appearing in combination with other colors, whether it be successive or simultaneously. Instead, however, of effecting changes in the objects taken in by the eye, we may study the mechanism of vision by investigating the disturbances of the function of sight itself under the influence of drugs injected into the eye, or in different ocular diseases. The latter method is by far the more valuable for revealing the real mechanism of the visual apparatus.
Similarly in the study of memory we may follow the method of the German school, such for instance as that of Ebbinghaus and others, and investigate the laws of memory by analyzing the changes effected in its contents; or we may study the mechanism of memory by studying its disturbances in different forms of amnesia and mental diseases. Since psychology primarily deals with the laws of psycho-physiological functions, it will be admitted that the more important and valuable method is the one that has for its subject matter the changes going on directly in the material under investigation. The investigations, however, of changes or disturbances of mental function itself are really a study of the abnormal, researches into the domain of mental pathology. In psychology, as in many other sciences, especially those of the biological order to which psychology naturally belongs, the pathological method is by far the most important. We can realize now the reason why it would be well for psychology to follow closely not the methods of physical sciences, but those of the biological sciences. The material with which physics deals lacks the pathological element, it can be introduced only figuratively, not so is it in the order of phenomena with which biology deals. In biology variations, abnormalities, pathological elements stand out in the foreground, and no step can be made without taking them into consideration. The psychologist in order to succeed and obtain more efficient and valuable results must keep in mind clearly the fact that the psychic process is a form of life in general, its phenomena are naturally related to the province of biology, and that of the highest part of it. The methods of psychological investigation must follow the line not of the physical, but of the biological sciences.
VIII The Spiritualistic and Materialistic Hypotheses
If we scrutinize more closely the science of psychology, we find that it is essentially dynamical in character. Consciousness is the subject matter of psychology; but consciousness is dynamic, it is first of all an activity, a process. Now all sciences that deal with processes cannot possibly help forming some working hypothesis that should unify the facts dealt with, and should above all be a guide for further research. Mechanics has its hypothesis of masses, forces, energy, inertia, conservation of matter and energy; thermotics its molecular energy; electricity its ether vibrations and currents; chemistry the affinity of atoms; dynamic physiology has its reflex processes; what is the fundamental hypothesis of psychology? We find the following hypotheses:
1 The Spiritualistic, or soul hypothesis,
2 The Materialistic hypothesis,
3 The Faculty hypothesis,
4 The Transmission hypothesis,
5 The Psycho-physiological hypothesis.The Metaphysical,The Positive.
We give here a brief review beginning with the spiritualistic hypothesis. At the very outset I must caution the reader against the grave error of confounding spiritualism with spiritism. The latter is a religious doctrine of life after death, and of the influences of natural or resurrected spirits; the former is a philosophical theory, hoary with age, that attempts to explain the phenomena of consciousness. Such men as Lotze and Ladd are ardent advocates of spiritualism. According to this hypothesis there exists a spiritual substance, a soul, that acts in all the processes of consciousness. The soul is the immutable principle that unifies all the phenomena of consciousness; in other words, all mental processes are but manifestations of the soul's activity. The medical man trained in the school of concrete physical sciences may smile, if not sneer, at the mention of the "soul." Such a hypothesis is in his opinion nothing but an anachronism. He may consider it as a theory long exploded by science and now only lingering among the lower ignorant classes, a theory which an intelligent scientist should be ashamed to introduce into his work even for the sake of discussion, and elucidation of his subject, the "soul" is nothing but superstition. To call a theory superstition does not refute it. The significant fact that Prof. Ladd in his volume on physiological psychology defends it valiantly, that Sigwart in his "Logic" takes up arms for it, and also that such a great thinker as Lotze, himself a medical man, takes it under his protection and finds it perfectly rational, and in fact the only tenable hypothesis, seems to show that there must be something in the "soul," and if superstition it be, it is one that has to be reckoned with, and not dismissed with contempt. We must, therefore, examine the reasons and facts that urge some thinkers and scientists to accept the soul as a working hypothesis for the phenomena of consciousness. There are two weighty considerations that are strongly in favor of spiritualism.
We have already pointed out in a previous discussion that mental phenomena are different in kind from those of the material world. A feeling, an idea, an image, a thought have neither length, nor breadth, nor height, nor weight; no psychic phenomenon can be expressed in terms of material magnitude. Hence, conclude the spiritualists, consciousness is different in kind from matter, it is a different substance, a soul.
Another great point upon which spiritualism rests is mental synthesis. We find that in consciousness, sensations, ideas, thoughts, feelings, are not juxtaposed as are the particles of some material body, but are in unity, in synthesis. The chair seen yonder consists of numerous impressions, sensations and ideas, but all these do not appear in consciousness in their bare separateness, but are synthetized in one percept, a chair. The various experiences that reach the mind, in spite of all their multitudinousness are still brought into relations and are unified, synthetized into the unity of consciousness, they are all referred to the same personality. Now reason the spiritualists, many different phenomena will remain in all their manifoldness and will not give rise to a unity, unless there is a medium through which they are unified. If a resultant is to be formed there must be something on which the forces that are to form the resultant, impinge. If then we do not assume the hypothesis of a spiritual substance, mental synthesis is incomprehensible, if not impossible.
We must now point out the weakness of the soul hypothesis. The argument of spiritualism, that because mental facts differ in kind from material facts, a spiritual substance must be assumed to exist is certainly fallacious. Phenomena may differ fundamentally and still we have no right whatever to conclude that they require two different substances. Time is different from space, but are they two different
