In conclusion, I should like to point out briefly some of the lessons of more general interest which may be learnt from the facts I have brought before you in these lectures. I hope that one result has been to convince you of the danger lying in the use of the _reductio ad absurdum_ argument when dealing with cultures widely different from our own. In the literature of the subject one often meets the adjectives “absurd” and “impossible” applied in some cases to social conditions in which the actual existence of the absurdities or impossibilities can be demonstrated. I may take as an example the argument of Mr. N. W. Thomas, which I have already mentioned, in which the classing of the maternal grandfather with the elder brother by the Dieri is regarded as reducing to an absurdity the contention that classificatory terms express ties of kinship. If Mr. Thomas had had a more lively faith in the social meaning of terms of relationship, he might have been led to notice that the Dieri marry the granddaughter of a brother, a fact he appears, in common with many other readers of Howitt, to have missed; one result of this marriage is to bring about just such a relationship as Howitt records without a man being his own great-uncle, as is supposed to be necessary by Mr. Thomas. Still another example may be taken from Professor Kroeber. He states that the classing together of the grandfather and the father-in-law which is found in the Dakota system, when worked out to its implications, would lead to the absurd conclusion that marriage with the mother was once customary among the Sioux. Here again, if Professor Kroeber had been less imbued with his belief in a purely linguistic and psychological chain of causation, and had been ready to entertain the idea that there might be a social meaning, he must have been led to see that the features of nomenclature in question would follow from other forms of marriage, and two of these, whatever their apparent improbability in America, cannot well be called absurd, since they are known to occur in other parts of the world. Following Riggs, Professor Kroeber does not specify which kinds of grandfather and father-in-law are classed together in Dakotan nomenclature, but in the full list given by Morgan, it is evident that one term is used for the fathers of both father and mother and for the fathers of both husband and wife. The classing of the father’s father with the wife’s father would be a natural result of marriage with the father’s sister, while the common nomenclature for father’s father and husband’s father would result from marriage with the brother’s daughter. It is not without significance that the features of nomenclature which would be the result of one or other, or of both these marriages, occur in a system which also bears evidence of the cross-cousin marriage, for these three forms of marriage occur in conjunction in one part of Melanesia, viz., the Torres Islands.