Here it may again be said: Leave the matter to the meta-physician and go on with your psychological work. I answer: The psychologist is not in the same position as the botanist or the zoölogist. He is studying mind in its relation to body. It cannot but be unsatisfactory to him to leave that relation wholly vague; and, as a matter of fact, he usually takes up with one theory or another. We have seen (section 36) that he may easily adopt a theory that leads him to overlook the great difference between physical phenomena and mental phenomena, and to treat them as though they were the same. This one may do in spite of all that introspection has to say about the gulf that separates them.
Psychology is, then, very properly classed among the philosophical sciences. The psychologist is not sufficiently sure of his materials to be able to dispense with reflective thought, in many parts of his field. Some day there may come to be a consensus of opinion touching fundamental facts, and the science may become more independent. A beaten track may be attained; but that has not yet been done.
70. THE DOUBLE AFFILIATION OF PSYCHOLOGY.—In spite of what has been said above, we must not forget that psychology is a relatively independent science. One may be a useful psychologist without knowing much about philosophy.
As in logic it is possible to write a text-book not greatly different in spirit and method from text-books concerned with the sciences not classed as philosophical, so it is possible to make a useful study of mental phenomena without entering upon metaphysical analyses. In science, as in common life, we can use concepts without subjecting them to careful analysis.
Thus, our common experience reveals that mind and body are connected. We may, for a specific purpose, leave the nature of this connection vague, and may pay careful attention to the physiological conditions of mental phenomena, studying in detail the senses and the nervous system. We may, further, endeavor to render our knowledge of mental phenomena more full and accurate by experimentation. In doing this we may be compelled to make use of elaborate apparatus. Of such mechanical aids to investigation our psychological laboratories are full.
It is to such work as this that we owe what is called the "physiological" and the "experimental" psychology. One can carry on such investigations without being a metaphysician. But one can scarcely carry them on without having a good knowledge of certain sciences not commonly supposed to be closely related to psychology at all. Thus, one should be trained in chemistry and physics and physiology, and should have a working knowledge of laboratory methods. Moreover, it is desirable to have a sufficient knowledge of mathematics to enable one to handle experimental data.
The consideration of such facts as these sometimes leads men to raise the question: Should psychology affiliate with philosophy or with the physical sciences? The issue is an illegitimate one. Psychology is one of the philosophical sciences, and cannot dispense with reflection; but that is no reason why it should not acknowledge a close relation to certain physical sciences as well. Parts of the field can be isolated, and one may work as one works in the natural sciences generally; but if one does nothing more, one's concepts remain unanalyzed, and, as we have seen in the previous section, there is some danger of actual misconception.
[1] "Psychology," Preface.