EVOLUTION 15 each evolving organism is a process gone through by all things." Science had shown that the universe, past and present, is subject to orderly changes ; he discovered that funda- mentally'this order is one. The nebular hy- pothesis proposed by Kant, confirmed by Her- schel and Laplace, and accepted by astrono- mers explained the origin and motions of suns and planets by slow condensation from a nebu- lous mist diffused through space. The geolo- gical history of our earth shows that it has un- dergone a vast series of progressive changes, and, as Prof. Dana says, " was first a feature- less globe of fire, then had its oceans and dry land, in course of time received mountains and rivers, and finally all those diversities of sur- face which now characterize it." The course of organic life, as we have seen, was a pro- gressive unfolding into greater diversity and specialty. Mind is developed with the body, and therefore mental phenomena obey a law of unfolding. As human society is made up of units that are capable of these changes, it presents in the past a gradual development of intelligence, arts, and institutions, as now em- bodied in our diverse and complex civilization. By a careful analysis of the phenomena in these widely separated cases, Mr. Spencer showed that they all conform to a great general law, of which individual life is but a special case. Equally in the inorganic, the organic, and the super-organic spheres, the progressive changes are from the homogeneous to the heteroge- neous by differentiation. But with increasing divergences there is also increasing definite- ness, coherence, complexity, and integration. Evolution is thus a universal law, while the development of the individual and the career of the race, so far from being exceptional phe- nomena, are but parts of the great system of change to which the whole cosmos conforms. Evolution being thus disclosed as a universal dynamical law, the question next arises, how is it to be interpreted ? Is it an ultimate law like gravitation, or is it a derivative principle deducible as a necessity from the established laws of matter, motion, and force? Mr. Spen- cer proves that evolution is a resultant of dy- namical agencies, and that, given matter as a vehicle of change, motion as the result of change, and force as the cause of change, such are their established laws of interaction that evolution follows as an inevitable consequence. We can here only touch upon the leading ele- ments of the elucidation, and must refer the reader to Mr. Spencer's "System of Philoso- phy" for the full elaboration of the subject. Modern science has established the great prin- ciples of the indestructibility of matter and the rvation of force. (See COEEELATION OF FORCES.) Mr. Spencer maintains that these resolve themselves into the single law of the persistence of force, and that this is the funda- mental postulate of evolution. Whatever in- terpretation is given to the principle, it cer- tainly becomes a fundamental condition of the 309 VOL. vii. 2 changes taking place in nature. If matter and force throughout the universe are neither cre- ated nor destroyed, all changes must be changes of transformation. The stock of material and energy being limited, each new effect must be at the expense of something preexisting; and hence in the ongoings of nature one thing is necessarily derived from another, while the problem of advance becomes one of trans- mutation. Mr. Spencer traces out the several causes of transformation or factors of evolu- tion, and shows that they are all corollaries from the supreme law of the persistence of force. Briefly indicated, these are as follows : 1. The principle of the rhythm of motion. Under the law of the persistence of forces and the diversity of their forms, there arise constant conflicts of effect, so that motions are not uniform but varying. Action is met by counteraction, and the result is that move- ments take a rhythmical form. Boughs, for example, sway in the wind, water is thrown into waves, sound arises in vibrations, earth- quakes are propagated in shocks, planets swing through eccentric orbits, breathing is recur- rent, the heart beats, scarcity alternates with abundance, and prices rise and fall. From the minutest organism throughout the whole frame of things to the most distant systems, from momentary pulses to geological cycles, the agitations of things take the form of thrills and surges, which produce incessant and uni- versal redistributions of matter and force. How are these redistributions directed? 2. They are controlled first by the law of the in- stability of the homogeneous. The relatively homogeneous is the commencing stage of all evolution, and Mr. Spencer has shown that this is an unstable condition, and under rhyth- mic disturbance tends constantly to rearrange- ment and greater complexity. No object can exist without being acted upon and altered by forces, and no mass can be thus acted upon in all parts alike ; unequal action therefore tends to destroy homogeneity and produce ever in- creasing diversity. For this cause the nebu- lous condition could not continue ; the homo- geneous germ divides into unlike parts ; a class of animals or plants distributed over a geo- graphical area, being unequally acted upon by environing conditions, would fall into diversity; and for the same reason a uniform social con- dition would be resolved into heterogeneous societies. 3. The transformations of evolu- tion are further explained by the dynamical principle of the multiplication of effects. Throughout all nature simple agencies produce diverse consequences, every impulse of force yielding a multiplicity of results. A simple mechanical collision of two bodies may pro- duce effects of sound, heat, light, electricity, and various chemical and structural changes ; an accident to the foot may entail a train of consequences affecting the whole constitution ; the upheaval of a continent may produce the most extensive alterations in the life of races ;
