Instead of starting from the fact that the natural sciences are possible only after abstracting from the subjective factors of experience, the more general problem of treating the contents of all experience in the most general way, is sometimes assigned to natural science. In such a case psychology is, of course, no longer coordinate with the natural sciences, but subordinate to them. Its problem is no longer to remove the abstraction employed by the natural sciences, and in this way to gain with them a complete view of experience, but it has to use the concept "subject" furnished by the natural sciences, and to give an account of the influence of this subject on the contents of experience. Instead of recognizing that an adequate definition of "subject" is possible only as a result of psychological investigations (sec. 1, 3a), a finished concept formed exclusively by the natural sciences is here foisted upon psychology. Now. for the natural sciences the subject identical with the body. Psychology is accordingly defined as the science which has to determine the dependence of immediate experience on the body. This position, which may be designated "psycho-physical materialism", is epistemologically untenable and psychologically unproductive. Natural science, which purposely abstracts from the subjective component of all experience, is at least in a position to give a final definition of the subject. A psychology that starts with such a purely physiological definition depends, therefore, not on experience but, just like the older materialistic psychology, on a metaphysical presupposition. The position is psychologically unproductive because, from the very first, it turns over the causal interpretation of psychical processes to physiology. But physiology has not yet furnished such an interpretation and never will be able to do so, because of the difference between the manner of regarding phenomena in natural science and in psychology. It is obvious, too, that such a form of psychology, which been turned into hypothetical brain-mechanics, con never be of any service as a basis for the mental sciences.
The strictly empirical trend of psychology, defined in the principles formulated above, is opposed to these attempts to renew metaphysical doctrines.
In calling it "voluntaristic", we are not to overlook the fact that, in itself, this psychological voluntarism has absolutely no connection with any metaphysical doctrine of will. Indeed it stands in opposition to Schopenhauer's one-sided metaphysical voluntarism, which derived all from being from a transcendental original will, and to the metaphysical systems of a Spinoza or a Herbart, which arose from intellectualism. In its relation to metaphysics, the characteristic of psychological voluntarism in the sense above defined, is its exclusion of all metaphysics from psychology. In its relations to other forms of psychology, it refuses to accept any of the attempts to reduce volitions to mere ideas, and at the same time emphasizes the typical character of volition for all psychological experience.
Volitional acts are universally recognized as occurrences, made up of a series of continual changes in quality and intensity. They are typical in the sense that this characteristic of being occurrences is held to he true for all the contents of psychical experience.
[1] Classics Editor's note: In the 3 rd Enlgish edition of Outlines (Judd, Trans, 1907), Wundt included the following short essays about sources for the various forms of psychology reviewed in this Introduction.
In their historical development many of these forms of psychology have grown up together. One may, however, mark off certain general sequences.
Thus, metaphysical forms have generally preceded empirical forms; descriptive forms have preceded explanatory; and finally, intellectualism has preceded voluntarism. The oldest work which treated of psychology as an independent science was ARISTOTLE'S work entitled "On the Soul". This work is to be classified as belonging to the dualistic group in its metaphysics, and to the group of facultypsychologies on the side of its empirical explanations.
(The soul was treated as the living principle in the body. There were three fundamental faculties, namely, alimentation, sensation, and thought,) Modern spiritualistic psychology begins with DESCARTES' dualism which recognizes two distinct forms of reality: first, the soul as a thinking and unextended entity, and second, matter as an extended and nonthinking reality. The Cartesian system found the point of contact between these two forms of reality in a particular region of the human brain, namely, the, pineal gland. The founder of modern materialism is THOMAS HOBBES (15881679).