Other questions, however, force themselves inevitably upon the attention of the inquiring student. Why is it that certain cultural materials are more widely and more rapidly diffused than others? Under what conditions does this diffusion take place and why does it take place at all? Finally, what is the ultimate source of customs, beliefs, languages, religious practices, and all the varied technical devices which compose the cultures of different peoples? What are the circumstances and what are the processes by which cultural traits are independently created? Under what conditions do cultural fusions take place and what is the nature of this process? These are all fundamentally problems of human nature, and as human nature itself is now regarded as a product of social intercourse, they are problems of sociology. The cultural processes by which languages, myth, and religion have come into existence among primitive peoples have given rise in Germany to a special science. Folk-psychology (_Völkerpsychologie_) had its origin in an attempt to answer in psychological terms the problems to which a comparative study of cultural materials has given rise. From two different directions ideas of folk-psychology have found their way into modern science. First of all there was a demand from the different social sciences [_Geisteswissenschaften_] for a psychological explanation of the phenomena of social life and history, so far as they were products of social [_geistiger_] interaction. In the second place, psychology itself required, in order to escape the uncertainties and ambiguities of pure introspection, a body of objective materials. Among the social sciences the need for psychological interpretation first manifested itself in the studies of language and mythology. Both of these had already found outside the circle of the philological studies independent fields of investigation. As soon as they assumed the character of comparative sciences it was inevitable that they should be driven to recognize that in addition to the historical conditions, which everywhere determines the concrete form of these phenomena, there had been certain fundamental psychical forces at work in the development of language and myth.[21]