Does it follow from the foregoing that there is no possible relation between psychology and culture, that psychological results are a matter of utter indifference to the ethnologist? In their desire to vindicate for their own branch of knowledge a place in the sun, some ethnologists have come very near, if they have not actually reached such a conclusion. To me the case appears in a somewhat different light. Whatever division of labor may be desirable for the economy of scientific work, knowledge as a whole knows nothing of watertight compartments. Further, the nominally distinct sciences are not subordinated to one another, but coexist in a condition of democratic equality and coöperativeness. We cannot reduce cultural to psychological phenomena any more than we can reduce biology to mechanics or chemistry, because in either case the very facts we desire to have explained are ignored in the more generalized formulation. But for specific purposes, the student of culture can call for aid upon each and all of the other branches of learning. It is a very important cultural problem whether the natives of South America knew the bronze technique, _i.e._, whether they consciously produced the observed alloy of copper and tin. But how can the ethnologist solve this problem? Only by requisitioning the services of the chemist. Now very few would deny that services of the kind rendered by chemistry can also be rendered to the study of culture by psychology. Indeed, most people would at once admit that the relationship with psychology is _a priori_ likely to be far more extensive and thorough-going. A few concrete examples will illustrate how this relationship may be conceived.