In addition to this we note Darwin's hypothesis of the origin of the species announced during the fifties. Natural science thus demonstrated the existence of a profound vital relationship, where man had previously seen nothing more than gaps and fragments, in a brilliant manner. The only question was as to what would be the bearing of these discoveries on the treatment of philosophic problems. The appropriation of the new views came most natural to positivism, and we have already seen how Herbert Spencer endeavored to incorporate them in his evolutional system.
The new impulse of natural science furnished the occasion for a large German literature of a materialistic trend, which had the effect of disseminating the ideas and discoveries of natural science very widely. About the middle of the nineteenth century the German literature of a materialists were supported in their opposition to dogmatics and spiritualistic speculations—as had been the case with their French precursors of the eighteenth century—by an idealistic movement based upon the interests of humanity and progress. It is to be observed that idealism is not incongruous with theoretical materialism: the materialist can consistently recognize the value of mental phenomena and efficiency, even though he does regard them as due to mere molecular changes.
The most noted writer in this movement is the physiologist, Jacob Moleschott (1822–1893), who was born in Holland, was Docent at Heidelberg in his youth, and, after being dismissed there on account of his views, went to Zurich and later to Italy, where he enjoyed a long and successful career as professor of physiology. In his book, Kreislauf des Lebens (1852), he extols chemistry as the highest science because it shows how matter—and to-
