To postulate an historical identity, however, on the basis of a number of common elements, in the face of numerous and important differences, implies a specific attitude toward the nature and significance of the common elements in these ceremonies. We know, indeed, that almost all theoreticians place greater insistence upon the similarities than upon the differences in cultural phenomena. There is perhaps a natural tendency to do so. But quite apart from this tendency, there must likewise be certain definite reasons for such an interpretation. It is essential, consequently, to understand at the very outset the theoretical justification of this position. II. THE INTERPRETATION OF THE COMMON ELEMENTS—SCHURTZ’S THEORY.—This question has been taken up _in extenso_ by Schurtz,[14] in his work on “Age Classes and Men’s Societies.” Here, as well as in previous theoretical discussions, the presence of a number of similarities has been considered sufficient for establishing the identity of a group of ceremonies that admittedly possess a large number of specific peculiarities. But Schurtz gives us a detailed psychological exposition (and in this lies perhaps his superiority over others who have discussed the same subject) of the reasons which have prompted him to take a certain attitude toward these “similarities.” If Schurtz’s work is therefore selected in preference to that of others, it is because of the fact that, in addition to practically taking the same position as most of the other theoreticians, he has most clearly defined some of the assumptions underlying their position. Schurtz’s line of argument seems to have been the following. An investigation of civilized as well as of primitive organizations has disclosed a number of similarities. Their historical development is unknown; but the enormous distance separating them geographically, precludes the possibility that these similarities have been due either to borrowing or to dissemination from some one original centre. They must consequently be explained by assuming that they have developed independently, as external manifestations of the unity of the human mind. We are thus led to the assumption accepted by most ethnologists to-day, that the human mind tends to express itself in similar modes of thought and action the world over. The variation in these modes is to be ascribed either to the differences in the nature of the geographical and social surroundings or to the emotional and intellectual individuality of different groups of people, or to both. We are, however, concerned here not so much with the variations as with the common modes of thought and action. It is consequently of prime importance to determine first the nature of these modes, their sequence, and the extent to which this sequence has been conditioned by the modes themselves.