Of course the materialistic challenge of the soul aroused great heat in theological circles. The personality of God and the nature of the soul became burning questions, and led to the dissolution of the Hegelian school into “the right wing” and “the left wing.” Hegel had always maintained his standing in orthodox circles as the Prussian “State philosopher.” Those followers who composed the “right wing” tried to interpret his doctrine in accordance with the traditional theological conception of the soul; the “left wing” interpreted Hegel as a pantheist, in whose doctrine the soul could not be considered as a substance with immortality. Feuerbach followed this by inverting Hegelianism into a nominalistic materialism, and conceived the soul as nature “in its otherness.” In 1854, at a convention of naturalists in Germany, the materialistic conception of the soul was found to be widely spread among the German physicians and naturalists. But the contradiction between the inferences of science and “the needs of the heart” became a subject of controversy, and in 1860, under the leadership of Kuno Fischer, the “return to Kant” was begun, which lasted throughout the nineteenth century. There are two names that stand out most prominently in relation to this controversy over the nature of the soul: they are those of Lotze (1817–1881) and Fechner (1801–1887). They are names that were conjured with by the generation of American scholars before the present. Lotze regarded the mechanical necessity of nature as the form in which the impulsive mental life of man realizes its purposes. Every soul therefore has a life that consists essentially in purposeful relations with other souls. And this is possible only if the lives of men are under an all-embracing Providence. Fechner chose another way to escape from the materialistic tendency. He regarded the soul and body as separate and qualitatively different, although exactly corresponding, manifestations of one unknown reality. There is a parallelism between the mental and the physical, in which the mental phenomena are known only to the individual perceiving them. As sensations are the surface waves of a total individual consciousness, so the consciousnesses of human beings are the surface waves of a universal consciousness. The mechanical activity of nature corresponds to the consciousness of God. We can investigate this correspondence by studying the correspondence between our own mental states and physical states. This is the modern well-known psychological method of psycho-physics. We can measure psychical quantities by formulating mathematical laws of their occurrence. Our present psychology has seen a development from all these earlier explanations; but this is a matter of contemporary writing and not of history.