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. CHAPTER XVIII ETHICS AND AESTHETICS 71. COMMON SENSE ETHICS.--We may, if we choose, study the actions of men merely with a view to ascertaining what they are and describing them accurately. Something like this is done by the anthropologist, who gives us an account of the manners and customs of the various races of mankind; he tells us _what is_; he may not regard it as within his province at all to inform us regarding _what ought to be_. But men do not merely act; they judge their actions in the light of some norm or standard, and they distinguish between them as right and wrong. The systematic study of actions as right and wrong yields us the science of ethics. Like psychology, ethics is a special science. It is concerned with a somewhat limited field of investigation, and is not to be confounded with other sciences. It has a definite aim distinct from theirs. And, also like psychology, ethics is classed as one of the philosophical sciences, and its relation to philosophy is supposed to be closer than that of such sciences as physics and mathematics. It is fair to ask why this is so. Why cannot ethics proceed on the basis of certain assumptions independently, and leave to some other discipline the whole question of an inquiry into the nature and validity of those assumptions? About half a century ago Dr. William Whewell, one of the most learned of English scholars, wrote a work entitled "The Elements of Morality," in which he attempted to treat the science of ethics as it is generally admitted that one may treat the science of geometry. The book was rather widely read a generation since, but we meet with few references to it in our time.