The foregoing instance, together with many others scattered through these lectures, will have pointed clearly to another lesson. In the present state of our knowledge a working scheme or hypothesis has largely to be judged by its utility. A way of regarding social phenomena which obstructs inquiry and leads people to overlook facts has its disadvantages, to say the least, while a scheme or hypothesis which leads people to worry out and discover things which do not lie on the surface will establish a strong claim on our consideration, even if it should ultimately turn out to be only the partial truth. I will give only one instance to illustrate how a belief in the dependence of the terminology of relationship on forms of marriage might act as a stimulus to research. In a system from the United Provinces recorded by Mr. E. A. H. Blunt in the Report of the last Indian Census, one term, _bahu_, is used for the son’s wife, for the wife, and for the mother.[35] Mr. Blunt puts on one side without hesitation the possibility that such common nomenclature can have been the result of any form of marriage, and ascribes it to the custom whereby a man and his wife live with the husband’s parents, in consequence of which the son’s wife, who is called _bahu_ by her husband, is also called _bahu_ by everyone else in the house. The causation of the common nomenclature which is thus put forward is a possible, perhaps even a probable, explanation. In such a case we should have a social chain of causation in which the son’s wife is called _bahu_ because she is one of a social group bound together by the ties of a common habitation. It can do no harm, however, to bear in mind as an alternative the possibility that the terminology may have arisen out of a form of marriage. It is evident that the use of a common term for the wife and the son’s wife would follow from a form of polyandry in which a man and his son have a wife in common. A further result of this form of marriage would be that the wife of the son, being also the wife of his father, would have the status of a mother.[36] We have no evidence for the presence of such a marriage in India, but our knowledge of the sociology of the more backward peoples of India is not so complete that we can afford to neglect any clue. The possibility suggested by the mode of using the term _bahu_ should lead us to look for other evidence of such a form of polyandry among the ruder elements of the population of India, of whose social structure our present knowledge is so fragmentary. [35] _Census of India_, 1911, vol. xv., p. 234. [36] In such a case the use of the term by other members of the household, including women, would be the result of a later extension of meaning.