[Footnote 1:  A critical exposition of the modern doctrine of development and of the causes used to explain it is given by Otto Hamann, Entwickelungslehre und Darwinismus, Jena, 1892.  Cf. also, O. Liebmann, Analysis der Wirklichkeit; and Ed. von Hartmann (above, p. 610). [Among the numerous works in English the reader may be referred to the article “Evolution,” by Huxley and Sully, Encyclopedia Britannica, 9th ed., vol. viii.; Wallace’s Darwinism, 1889; Romanes, Darwin and after Darwin, i. The Darwinian Theory, 1892; and Conn’s Evolution of To-day, 1886.—­TR.]]

[Footnote 2:  Cf.  Liebmann, Analysis der Wirklichkeit, 2d ed., pp. 53-59.  G. Frege (Begriffsschrift, 1879; The Foundations of Arithmetic, 1884; Function and Concept, 1891; “On Sense and Meaning” in the Zeitschrift fuer Philosophie, vol. c. 1892) has also chosen the region intermediate between mathematics and philosophy for his field of work.  We note, further, E.G.  Husserl, Philosophy of Arithmetic, vol. i., 1891.]

[Footnote 3:  Ernst Haeckel of Jena (born 1834; General Morphology, 1866; Natural History of Creation, 1868 [English, 1875] I Anthropogeny, 1874; Aims and Methods of the Development History of To-day, 1875; Popular Lectures, 1878 seq.—­English, 1883), G. Jaeger, A. Schleicher (The Darwinian Theory and the Science of Language, 1865), Ernst Krause (Carus Sterne, the editor of Kosmos) O. Caspari, Carneri (Morals and Darwinism, 1871), O. Schmidt, Du Prel, Paul Ree (The Origin of the Moral Feelings, 1877; The Genesis of Conscience, 1885; The Illusion of Free Will, 1885); G.H.  Schneider (The Animal Will, 1880; The Human Will, 1882; The Good and III of the Human Race, 1883).]

Besides the theory of knowledge, in the elaboration of which the most eminent naturalists[1] participate with acuteness and success, psychology and the practical disciplines also betray the influence of the scientific spirit.  While sociology and ethics, following the English model, seek an empirical basis and begin to make philosophical use of statistical results (E.F.  Schaeffle, Frame and Life of the Social Body, new ed., 1885; A. von Oettingen, Moral Statistic in its Significance for a Social Ethics, 3d ed., 1882), psychology endeavors to attain exact results in regard to psychical life and its relation to its physical basis—­besides Fechner and the Herbartians, W. Wundt and A. Horwicz should be mentioned here.  Wundt and, of late, Haeckel go back to the Spinozistic parallelism of material and psychical existence, only that the latter emphasizes merely the inseparability (Nichtohneeinander) of the two sides (the cell-body and the cell-soul) with a real difference between them and a metaphysical preponderance of the material side, while the former emphasizes the essential unity of body and soul, and the higher reality of the spiritual side.