It is the same scientific spirit of the time, which in the fifties led many who were weary of the idealistic speculations over to materialism, that now secures such wide dissemination and so widespread favor for the endeavors of the neo-Kantians and the positivists or neo-Baconians, who desire to see metaphysics stricken from the list of the sciences and replaced by noetics, and the theory of the world relegated to faith.  The philosophy of the present, like the pre-Socratic philosophy and the philosophy of the early modern period, wears the badge of physics.  The world is conceived from the standpoint of nature, psychical phenomena are in part neglected, in part see their inconvenient claims reduced to a minimum, while it is but rarely that we find an appreciation of their independence and co-ordinate value, not to speak of their superior position.  The power which natural science has gained over philosophy dates essentially from a series of famous discoveries and theories, by which science has opened up entirely new and wide outlooks, and whose title to be considered in the formation of a general view of reality is incontestable.  To mention only the most prominent, the following have all posited important and far-reaching problems for philosophy as well as for science:  Johannes Mueller’s (Mueller died 1858) theory of the specific energies of the senses, which Helmholtz made use of as an empirical confirmation of the Kantian apriorism; the law of the conservation of energy discovered by Robert Mayer (1842, 1850; Helmholtz, 1847, 1862), and, in particular, the law of the transformation of heat into motion, which invited an examination of all the forces active in the world to test their mutual convertibility; the extension of mechanism to the vital processes, favored even by Lotze; the renewed conflict between atomism and dynamism; further, the Darwinian theory[1] (1859), which makes organic species develop from one another by natural selection in the struggle for existence (through inheritance and adaptation); finally, the meta-geometrical speculations[2] of Gauss (1828), Riemann (On the Hypotheses which lie at the Basis of Geometry, 1854, published in 1867), Helmholtz (1868), B. Erdmann (The Axioms of Geometry, 1877).  G. Cantor, and others, which look on our Euclidean space of three dimensions as a special case of the unintuitable yet thinkable analytic concept of a space of n dimensions.  The circumstance that these theories are still largely hypothetical in their own field appears to have stirred up rather than moderated the zeal for carrying them over into other departments and for applying them to the world as a whole.  Thus, especially, the Darwinians[3] have undauntedly attempted to utilize the biological hypothesis of the master as a philosophical principle of the world, and to bring the mental sciences under the point of view of the mechanical theory of development, though thus far with more daring and noise than success.  The finely conceived ethics of Hoeffding (p. 585) is an exception to the rule which is the object of this remark.