Aside from his theory of evolution, in his principal thesis, which he fairly sustains by powerful argument, Dargun has rendered to science a distinct service. It is, he insists, highly necessary carefully to distinguish between _power_ and _relationship_. "Mother-right" does not involve "maternal power" or the matriarchate, though sometimes actually united with it; nor does the headship of the house-father as provider, protector, and master imply agnation, the so-called "father-right." There is no contrast between power and relationship. "Mother-right in the sense of exclusive maternal kinship is compatible with a patriarchate just as exclusive." They may, and often do, coexist. It follows that the presence of the maternal system of kinship does not imply the existence of maternal power; just as it does not imply the non-existence of paternal authority. The distinction between power and kinship is justly declared to be an "indispensable key" for the solution of the greatest difficulties arising in this branch of sociological science, the disregard of which has often vitiated or confused the argument even of the foremost investigators.[54] With the aid of his key Dargun examines the linguistic evidence, which he finds favorable to the existence of mother-right among all the Aryan peoples after the separation, though united with a real supremacy of the house-father;[55] and he protests vigorously against the tendency, even on the part of Leist, to confound old Indic with old Aryan law; for the "Indians of the Vedas are in many respects more advanced than the Germans a thousand or the Slavs two thousand years later."[56] Valuable as the criticism of Dargun undoubtedly is, notably his distinction between power and relationship, it can scarcely be admitted that he has done more than reopen the question of the existence at any time of mother-right among the Aryans. His results are negative. He has not shifted the burden of proof; while his argument tends to confirm the view of the philologists that from the primitive stage the Aryan father was head of the household.[57] [54] _Ibid._, 3 ff., 28, 36, 86 ff., 155, _passim_. As remarked in the text, the whole work is concerned with the thesis in question. The distinction is also made in the _Mutterrecht und Raubehe_, 18. [55] See _Mutterrecht und Vaterrecht_, 86-116, for his criticism of the linguistic argument. [56] _Ibid._, 91, 92. _Cf._ a similar protest against conclusions as to the primitive Aryans derived from Greek and Roman sources, _ibid._, 116; and _Mutterrecht und Raubehe_, 14.