[284] This obviously does not imply that the naturalist should not investigate Nature’s processes, and not only correlate these, but also work them up into a universal conception; this is indeed both desirable and necessary if natural knowledge is to be regarded in its true value. The naturalist by this means becomes a philosopher, and the vitality of the so-called “natural philosopher” has been inspired, not by the necessity for investigation, but by philosophy proper. [285] [The discovery here referred to is the synthesis of urea by Wöhler in 1828 (Pogg. Ann. xii., 253; xv. 619), by the molecular transformation of ammonium cyanate. Since that period large numbers of organic syntheses have been effected by chemists, and many of the compounds formerly supposed to be essential products of life have been built up in the laboratory from their inorganic elements. The division of chemistry into “organic” and “inorganic” is thus purely artificial, and is merely retained as a matter of convenience, the former division of the science being defined as the chemistry of the carbon compounds. R.M.] [286] “Wahreit und Irrthum im Darwinismus.” Berlin, 1875. [287] [Eng. ed. I have been reproached by competent authorities for having clothed my ideas upon the theory of selection in the form of a reply to Von Hartmann. I willingly admit that this author cannot be considered as the leader of existing philosophical views upon the theory of descent in Germany; Frederick Albert Lange has certainly a much greater claim to this position. Lange does not however combat this theory; he accepts and develops it most beautifully and lucidly on a sound philosophical basis in such a manner as has never been done before from this point of view (“Geschichte des Materialismus,” 3rd. ed., 1877, vol. ii. pp. 253-277). On most points I can but agree with Lange. Von Hartmann, however, whose objections appeared to me to be supported by a wide scientific knowledge, afforded me a suitable opportunity of developing my own ideas upon some essential points in the theory of selection. In this sense only have I attempted to interfere with this author, the refutation of his views, as such, having been with me a secondary consideration.] [The chief exponent of the doctrine of organic evolution in this country is Mr. Herbert Spencer, in whose “Principles of Biology,” vol. i. chap. xii., will be found a masterly treatment of the theory of descent from a “mechanical” point of view. R.M.] [288] [The above views on the nature of variability, which were also broadly expressed in the first essay “On the Seasonal Dimorphism of Butterflies” (pp. 114, 115), are fully confirmed by Herbert Spencer (_loc. cit._ chaps. ix. and x.), and more recently by A. R. Wallace in an article on “The Origin of Species and Genera” (_Nineteenth Century_, vol. vii., 1880, p. 93). See also some remarks by Oscar Schmidt in his “Doctrine of Descent and Darwinism,” Internat. Scien. Ser. 3rd. ed. 1876, p. 173. R.M.]