The aim of folk-psychology has been, on the whole, to explain the genesis and development of certain cultural forms, i.e., language, myth, and religion. The whole matter may, however, be regarded from a quite different point of view. Gabriel Tarde, for example, has sought to explain, not the genesis, but the transmission and diffusion of these same cultural forms. For Tarde, communication (transmission of cultural forms and traits) is the one central and significant fact of social life. "Social" is just what can be transmitted by imitation. Social groups are merely the centers from which new ideas and inventions are transmitted. Imitation is the social process. There is not a word that you say, which is not the reproduction, now unconscious, but formerly conscious and voluntary, of verbal articulations reaching back to the most distant past, with some special accent due to your immediate surroundings. There is not a religious rite that you fulfil, such as praying, kissing the icon, or making the sign of the cross, which does not reproduce certain traditional gestures and expressions, established through imitation of your ancestors. There is not a military or civil requirement that you obey, nor an act that you perform in your business, which has not been taught you, and which you have not copied from some living model. There is not a stroke of the brush that you make, if you are a painter, nor a verse that you write, if you are a poet, which does not conform to the customs or the prosody of your school, and even your very originality itself is made up of accumulated commonplaces, and aspires to become commonplace in its turn. Thus, the unvarying characteristic of every social fact whatsoever is that it is imitative. And this characteristic belongs exclusively to social facts.[22] Tarde's theory of transmission by imitation may be regarded, in some sense, as complementary, if not supplementary, to Wundt's theory of origins, since he puts the emphasis on the fact of transmission rather than upon genesis. In a paper, "Tendencies in Comparative Philology," read at the Congress of Arts and Sciences at the St. Louis Exposition in 1904, Professor Hanns Oertel, of Yale University, refers to Tarde's theory of imitation as an alternative explanation to that offered by Wundt for "the striking uniformity of sound changes" which students of language have discovered in the course of their investigation of phonetic changes in widely different forms of speech.