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.

[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 Morph