Especially if on the part of the field ethnographers there could be expected some interest in the results of theoretical research, such indications of contradictions on points, the theoretical importance of which should be proved, would be of real value.[37] Only such a co-operation between theoretical writers and observers can give us satisfactory results. To make indifferent observation is easy. To note essential things and give useful observations is impossible without theoretical knowledge and an insight into the laws of sociology. It would be better if field ethnographers would consider the questions of theoretical writers, and take into account in their scheme of investigations the utilization subsequently to be made of their work. [37] Mr. Thomas in his work on Australian kinship suggests at every step questions which apparently are quite within the scope of investigation, and upon which our present evidence gives no answer. But unhappily I have not been able to trace any influence of this important work in the recent ethnographic publications. Returning, after this digression, to our theme, it may be observed that the method of dealing with evidence is very simple: there is the analytical operation, of finding the essential points contained in a series of statements; in other words, the operation of analyzing these statements into simple factors and stating which are common to all the statements and may be accepted as well established. A further task consists in pointing out the irreducible contradictions. This operation obviously contains all the others--criticism of the text and contents of the statement, and reduction of contradictions to local differences. It is evident also that, although theoretically the criticism of statements was dealt with first, then the question of geographical differences, and in the third place the problem of handling a series of statements, as a matter of fact, the first step is to make a survey of all our evidence, resolving it into a set of problems, and then to take each problem separately; in this way we shall find contradictions and endeavour to eliminate them, and we shall be compelled to exercise criticism on the statements.