764 EVOLUTION the biological sciences which has made us familiar with the simplest types and elements of organism; finally, to the recent development of the science of anthropology (includ ing comparative psychology, philology, &c.), and to the vast extension and improvement of all branches of historical study. English Writers Darwin. The honour of working out this theory of evolution on a substanial basis of fact belongs to England. Of the writers who have achieved this result Mr Darwin deserves the first notice. Though modestly confining himself to the problem of accounting for the evolution of the higher organic forms out of the lower, Mr Darwin has done much to further the idea of a gradual evolution of the physical world. The philosophic significance of the hypothesis of natural selection, especially associated with Mr Darwin, is due, as Professor Helmholtz points out, to the fact that it introduces a strictly me chanical conception in order to account for those intricate arrangements known as organic adaptations which had before been conceived only in a teleological manner. By viewing adaptations as conditions of self-preservation, Mr Darwin is able to explain how it is that the seemingly pur poseful abounds in organic nature. In so doing he has done much to eliminate the teleological method from biology. It is true that, in his conception of seemingly spontaneous variations and of correlations of growth, he leaves room for the old manner of viewing organic development as controlled by some internal organizing principle. Yet his theory, as a whole, is clearly a heavy blow to the teleological method. Again, Mr Darwin has greatly extended the scope of mechanical interpretation, by making intelligible, apart from the co-operation of intelligent purpose, the genesis of the organic world as a harmonious system of distinct groups, a unity in variety, having certain well-marked typical affinities. How greatly this arrangement has helped to support the idea of an ideal plan, we have had occasion to observe. Mr Darwin in his doctrine of the organic world as a survival refers this appearance of systematic plan to perfectly natural causes, and in so doing he gives new mean ing to theancient theory that the harmony of the world arises out of discord. Once more, Mr Darwin s hypothesis is of wide philosophic interest, since it helps to support the idea of a perfect gradation in the progress of things. The variations which he postulates are slight, if not infinitesimal, and only effect a sensible functional or morphological change after they have been frequently repeated and accumulated by heredity. Mr Darwin s later work, in which he applies his theory of the origin of species to man, is a valuable contribution to a naturalistic conception of human development. The mind of man in its lowest stages of development is here brought into close juxtaposition to the animal mind, and the upward progress of man is viewed as effected by natural causes, chief among which is the action of natural selection. Mr Darwin does not inquire into the exact way in which the mental and the bodily are connected. He simply assumes that, just as the bodily organism is capable of vary ing in an indefinite number of ways, so may the mental faculties vary indefinitely in correspondence with certain physical changes. In this way he seeks to account" for all the higher mental powers, as the use of language and reason, the sentiment of beauty, and conscience. Finally, Mr Darwin seeks to give a practical and ethical turn to his doctrine. He appears to make the end of evolu tion the conscious end of man s action, since he defines the general good as "the rearing of the greatest number of individuals in full health and vigour, and with all their faculties perfect under the conditions to which they are subject." Further, in his view of the future of the race, Mr Darwin leans to the idea that the natural process which has effected man s first progress must continue to be an important factor in evolution, and that, consequently, it is not well to check the scope of this process by undue restraints of population, and a charitable preservation of the incompetent. A. .A . Wallace. Mr A. R. Wallace, who shares with Mr Darwin the honour of establishing the doctrine of natural selection, differs from the. latter in setting much narrower limits to the action of this cause in the mental as well as the physical domain. Thus he would mark off the human faculty of making abstractions, such as space and time, as powers which could not have been evolved in this way. Mr Wallace leans to the teleological idea of some superior principle which has guided man in his upward path, as well as controlled the whole process of organic evolution. This law is connected with the absolute origin of life and organization. Herbert Spencer. The thinker who has done more than any one else to elaborate a consistent philosophy of evolu tion on a scientific basis is Mr Herbert Spencer. First of all b.3 seeks to give greater precision to the conception of this universal process. Evolution is a change from the homogeneous to the heterogeneous, from the indefinite or undetermined to the definite or determined, from the inco herent to the coherent. Again, Mr Spencer seeks to show that the causes of evolution are involved in the ultimate laws of matter, force, and motion, among which he gives great prominence to the modern doctrine of the conservation of energy. Thus the rationale of the process shapes itself to Mr Spencer as a distinctly mechanical problem. He sets out with the assumption of a limited mass of homo geneous matter acted upon by incident forces, and seeks to show how, by help of two laws, namely, the instability of the homogeneous, and the multiplication of the effects of any such incident force, the process known as evolution is brought about. This process is illustrated in the genesis of the solar system,- for the explanation of which Mr Spencer makes use of the nebular hypothesis, in the formation of our planet, as well as the development of organic and mental life. Mr Spencer does not, however, conceive of this process of evolution as unlimited in time. As in the development of the individual organism, so in that of organic beings as a whole, of the earth, and of the solar system, there is a conflict between the forces of which the action is integrating or consolidating and those of which the action is disintegrating. The process of evolution always tends to an equilibration between these conflicting forces and ultimately to a dissolution of the products of evolution. Thus the solar system is a moving equilibrium which is destined to be finally dissipated into the attenuated matter out of which it arose. Mr Spencer thus approaches the earliest theories of cosmic evolution when he tells us (First Principles, p. 482) that vast periods in which the forces of attraction pre vail over those of repulsion, alternate with other vast periods in which the reverse relation holds. The mechani cal theory of evolution thus laid down in the First Principles is applied in Mr Spencer s later works to the explanation of organic, mental, and social evolution. The full explanation of the processes of inorganic evolution finds no place in the writer s system. Mr Spencer seeks, in the Principles of Biology, to conceive of organic bodies and their actions in mechanical terms. Life te regarded as essentially a correspondence of internal actions in the organism to external actions proceeding from the environ ment, and the object of Mr Spencer s volumes is to explain on mechanical principles the growth of this correspond- 1 The writer suggests that the whole sidereal system may be the
result of a similar process.