Spencer himself most clearly realized the insufficiency of the law of evolution alone, for he asks, "May we seek for some all-pervading principle which underlies this all pervading process!"[A] and proceeds to search out this "all-pervading principle" which at last he determines to be the persistence of force--the operation of the universal, indestructible, incomprehensible force, which appears as gravitation, light, heat, electricity, magnetism, chemical affinity and in other forms.[B] [Footnote A: First Principles, p. 408.] [Footnote B: Loc. cit., p. 494.] [Sidenote: Evolution does not admit a final death.] A natural question now is, Is there any limit to the changes undergone by matter, and which we designate as evolution? "Will they go on forever? or will there be an end to them?"[A] As far as our knowledge goes, there is an end to all things, a death which is the greatest known change, and as far as human experience goes, all things tend toward a death-like state of rest. That this rest is permanent is not possible under law of evolution; for it teaches that an ulterior process initiates a new life; that there are alternate eras of evolution and dissolution. "And thus there is suggested the conception of a past during which there have been successive evolutions analogous to that which is now going on; and a future during which successive other such evolutions may go on ever the same in principle but never the same in concrete result."[B] This is practically the same as admitting eternal growth. [Footnote A: Loc. cit., p. 496.] [Footnote B: Loc. cit., p. 550.] The final conclusion is that "we can no longer contemplate the visible creation as having a definite beginning or end, or as being isolated. It becomes unified with all existence before and after; and the force which the universe presents falls into the same category with space and time, as admitting of no limitation in thought."[A] [Footnote A: Loc. cit., p. 564.] [Sidenote: Spirit and matter are alike.] It is interesting to note the conclusion concerning spirit and matter, to which Mr. Spencer is led by the law of evolution. "The materialist and spiritualist controversy is a mere war of words, in which the disputants are equally absurd--each thinking that he understands that which it is impossible for any man to understand. Though the relation of subject and object renders necessary to us these antithetical conceptions of spirit and matter; the one is no less than the other to be regarded as but a sign of the Unknown Reality which underlies both."[A] [Footnote A: First Principles, pp. 570 and 572.] While the law of evolution, as formulated by Spencer and accepted by the majority of modern thinkers, is the nearest approach to the truth possessed by the world of science, yet there is no disposition on the part of the writer to defend the numerous absurdities into which Spencer and his followers have fallen when reasoning upon special cases.