But over and above clearing up some contradictions, solving some difficulties, and filling up a gap in the information concerning Australian kinship organization, there is a much deeper justification for a detailed collection and classification of facts referring to the individual family in Australia. I mean, it is only such a proceeding that can give us a scientific, correct and useful definition of the Australian individual family (or any other social unit in general). _A priori_ only a vague meaning can be attached to the term "individual family," when it refers to a society different from ours. For the essential features of the individual family, as of all other social institutions, depend upon the general structure of a given society and upon the conditions of life therein. A careful and detailed analysis of the family life and of the different aspects of the family unit in connection with other social phenomena is therefore necessary. Such an analysis enables us to describe the said unit in a complete and exact way. It is Dr. Rivers to whom we are indebted for emphasizing the methodological standpoint in this connection. In his article[17] he points out that we cannot _a priori_ assert the existence of even such an apparently unquestionable fact as individual motherhood in every human society whether actual or hypothetical. To affirm that in a given society motherhood is individual and not communal (group motherhood), a strict analysis of a whole series of circumstances is necessary. Applying Dr. Rivers' argument to the other family relationships, we may say that all the circumstances referring to the relation between man and wife, parents and children, brothers and sisters, must be submitted to a careful and detailed analysis; and that only such an examination can give us the right idea of what may be called the individual family in a given society--in this case the Australian individual family.[18] [17] _Anthrop. Essays_, pp. 309 _sqq._ [18] Comp. below, p. 206, the second paragraph of footnote 1.