If you concede the causal relation between the characteristic features of a Fijian or Anaiteum or Guadalcanar system and the cross-cousin marriage, there can be no question that it is the cross-cousin marriage which is the antecedent and the features of the system of relationship the consequences. I do not suppose that, even in this subject, there will be found anyone to claim that the Fijians took to marrying their cross-cousins because such a marriage was suggested to them by the nature of their system of relationship. We have to do in this case, not merely with one or two features which might be the consequence of the cross-cousin marriage, but with a large and complicated meshwork of resemblances and differences in the nomenclature of relationship, each and every element of which follows directly from such a marriage, while no one of the systems I have considered possesses a single feature which is not compatible with social conditions arising out of this marriage. Apart from quantitative verification, I doubt whether it would be possible in the whole range of science to find a case where we can be more confident that one phenomenon has been conditioned by another. I feel almost guilty of wasting your time by going into it so fully, and should hardly have ventured to do so if this case of social causation had not been explicitly denied by one with so high a reputation as Professor Kroeber. I hope, however, that the argument will be useful as an example of the method I shall apply to other cases in which the evidence is less conclusive.