that terms of relationship reflect psychology, not sociology, or, in other words, that the way in which terms of relationship are used depends on a chain of causation in which psychological processes are the direct antecedents of this use. I will try to make his meaning clear by means of an instance which he himself gives. He says that at the present time there is a tendency among ourselves to speak of the brother-in-law as a brother; in other words, we tend to class the brother-in-law and the brother together in the nomenclature of our own system of relationship. He supposes that we do this because there is a psychological similarity between the two relationships which leads us to class them together in our customary nomenclature. I shall return both to this and other of his examples later.
We have now seen that the opponents of Morgan have taken up two main positions which it is possible to attack: one, that the classificatory system is nothing more than a body of terms of address; the other, that it and other modes of denoting relationship are determined by psychological and not by sociological causes. I propose to consider these two positions in turn.
Morgan himself was evidently deeply impressed by the function of the classificatory system of relationship as a body of salutations. His own experience was derived from the North American Indians, and he notes the exclusive use of terms of relationship in address, a usage so habitual that
