reich,[1] under the title of convergence. According to this view a definite culture complex, which appears to be the same among two or more social groups, may prove upon analysis to have been arrived at in quite different ways.[2] The similarity is in this case merely an accident of development. As the reality of such convergence has been clearly established for certain instances, it must always be considered as a possible factor, and so complicates our problem. It has, however, one great virtue in that its applicability must be empirically determined for each case, and can not be deduced from a general presupposition. In fact, all these theories are of little use as formulæ of interpretation, for we must study carefully each trait-complex before a conclusion as to its origin can be reached. Their true functions are to define the different ways in which cultural similarities have been observed to come about.
The intensive analytic study of single trait-complexes has developed the pattern theory.[3] The conception is that in certain phases of culture each social unit develops a style, or pattern, for its traits and that borrowed traits will be worked over to make them conform to this pattern. So far as we can now see such patterns hold only for organized traits like ceremonies and social systems of control. The very complete studies we now have for the cultures of a few tribes in the central part of North America suggest that in organized ceremonies each tribe has one main concept according to which all their ritualistic performances are adjusted. For example, we find that the Dakota have a conception that supernatural power comes by a vision or dream, in which an animal-like being designates a plant as containing the power sought, and this plant then becomes the important objective part of the ritual. The Menomini, on the other hand, consider that power is conveyed by a song and that the true supernatural experience is to be found only when a song is handed down. The rituals of each also have distinct forms or styles of composition by which they can be distinguished. Yet, so far as we have observed, these tribal pattern conceptions do not greatly interfere with the absorption of foreign rituals. For example,
