Just as among most peoples of rude culture the clan or other exogamous group is the essential unit of social organisation, so among ourselves this social unit is the family, using this term for the group consisting of a man, his wife, and their children. If we examine our terms of relationship, we find that those applied to individual persons and those used in a narrow and well-defined sense are just those in which the family is intimately concerned. The terms father, mother, husband and wife, brother and sister, are limited to members of the family of the speaker, and the terms father-, mother-, brother-, and sister-in-law to the members of the family of the wife or husband in the same narrowly restricted sense. Similarly, the terms grandfather and grandmother are limited to the parents of the father and mother, while the terms grandson and granddaughter are only used of the families of the children in the narrow sense. The terms uncle and aunt, nephew and niece, are used in a less restricted sense, but even these terms are only used of persons who stand in a close relation to the family of the speaker. We have only one term used with anything approaching the wide connotation of classificatory terms of relationship, and this term is used for a group of relatives who have as their chief feature in common that they are altogether outside the proper circle of the family and have no social obligations or privileges. They are as eligible for marriage as any other members of the community, and only in the very special cases I considered in the first lecture are they brought into any kind of legal relation. The dependence of our own use of terms of relationship on the social institution of the family seems to me so obvious that I find it difficult to understand how anyone who has considered these terms can put forward the view that the terminology of relationship is not socially conditioned. It seems to me that we have only to have the proposition stated that the classificatory system and our own are the outcome of the social institutions of the clan and family respectively for the social causation of such terminology to become conspicuous. I find it difficult to understand why it has not long before this been universally recognised. I do not think we can have a better example of the confusion and prejudice which have been allowed to envelop the subject through the unfortunate introduction of the problem of the primitive promiscuity or monogamy of mankind. It is not necessary to have an expert knowledge of the classificatory system. It is only necessary to consider the terms we have used almost from our cradles in relation to their social setting to see how the terminology of relationship has been determined by that setting.