Still nearer do we come toward realizing the unity of Nature when we recollect that the law of evolution is not only the same for all these various worlds, but is also the same throughout all other orders of phenomena. Not only in the development of cosmical bodies, including the earth, but also in the development of life upon the earth's surface and in the special development of those complex manifestations of life known as human societies, the most general and fundamental features of the process are the same, so that it has been found possible to express them in a single universal formula. And what is most striking of all, this notable formula, under which Herbert Spencer has succeeded in generalizing the phenomena of universal evolution, was derived from the formula under which Von Baer in 1829 first generalized the mode of development of organisms from their embryos. That a law of evolution first partially detected among the phenomena of the organic world should thereafter not only be found applicable to all other orders of phenomena, but should find in this application its first complete and coherent statement, is a fact of wondrous and startling significance. It means that the universe as a whole is thrilling in every fibre with Life,--not, indeed, life in the usual restricted sense, but life in a general sense. The distinction, once deemed absolute, between the living and the not-living is converted into a relative distinction; and Life as manifested in the organism is seen to be only a specialized form of the Universal Life. The conception of matter as dead or inert belongs, indeed, to an order of thought that modern knowledge has entirely outgrown. If the study of physics has taught us anything, it is that nowhere in Nature is inertness or quiescence to be found. All is quivering with energy. From particle to particle without cessation the movement passes on, reappearing from moment to moment under myriad Protean forms, while the rearrangements of particles incidental to the movement constitute the qualitative differences among things. Now in the language of physics all motions of matter are manifestations of force, to which we can assign neither beginning nor end. Matter is indestructible, motion is continuous, and beneath both these universal truths lies the fundamental truth that force is persistent. The farthest reach in science that has ever been made was made when it was proved by Herbert Spencer that the law of universal evolution is a necessary consequence of the persistence of force. It has shown us that all the myriad phenomena of the universe, all its weird and subtle changes, in all their minuteness from moment to moment, in all their vastness from age to age, are the manifestations of a single animating principle that is both infinite and eternal.