By the end of the nineteenth century the new developmental view prevailed. In modern society a new concept has taken its place beside the fact of puberty. This is the concept of "adolescence." First given classic expression by G. Stanley Hall in the 1890s, he then stated the concept emphatically in 1904 in his two-volume work, Adolescence. Hall's perspective was Darwinian, although he saw man's evolution as having shifted from the physical to the psychological plane. Adolescence is a new birth, for the higher and more completely human traits are now born. The qualities of body and mind that now emerge are far newer. The "new birth," however, is not easy. It involves a good deal of difficulty and even despair, and is attended by depression and melancholy. Besides viewing adolescence symbolically and scientifically, Hall seems also to have located it within the tradition of religious conversion.