By the word kinship, roughly speaking, is denoted a series of family relationships (those of parents to children, brothers to sisters, etc.), all of which consist of a set of extremely complex phenomena. They are made up of the most heterogeneous elements: physiological (birth, procreation, suckling, etc.), social (community of living, of interests, social norms, etc.), and psychological (different ways in which these relations are conceived, different moral ideas, and different types of feelings). Special care must be taken to select in all these elements the essential ones, as an omission would be just as fatal for the investigations as an overburdening with secondary elements. Moreover, it would be specially valuable to look at all these heterogeneous determining elements from the same point of view, and view them all under one and the same aspect. Leaving on one side the purely physiological problem of kinship,[514] it appears necessary to give a sociological view of kinship, _i. e._ to show the social bearing of physiological facts as well as of psychological elements. But it appears also necessary to view the whole of the phenomena of kinship from the psychological point of view; that is, to show how the sociological and physiological facts of kinship are reflected in the "collective mind" of the given society. [514] This would be the place to point out the biological meaning of the social aspects of kinship and family; whether, _e. g._ the different social regulations of sexual intercourse, which in higher societies afford the basis to kinship, the different forms of family and kinship are the expression of biological laws. How far such would be possible could only be decided on the basis of a biological knowledge which the present writer does not possess.