We have seen that before men could arrive at the idea of God, before out of the old crude and fragmentary polytheisms there could be developed a pure and coherent theism, it was necessary that physical generalization should have advanced far enough to enable them, however imperfectly, to reason about the universe as a whole. It was a faint glimpse of the unity of Nature that first led men to the conception of the unity of God, and as their knowledge of the phenomenal fact becomes clearer, so must their grasp upon the noumenal truth behind it become firmer. Now the whole tendency of modern science is to impress upon us ever more forcibly the truth that the entire knowable universe is an immense unit, animated throughout all its parts by a single principle of life. This conclusion, which was long ago borne in upon the minds of prophetic thinkers, like Spinoza and Goethe, through their keen appreciation of the significance of the physical harmonies known to them, has during the last fifty years received something like a demonstration in detail. It is since Goethe's death, for example, that it has been proved that the Newtonian law of gravitation extends to the bodies which used to be called fixed stars. That such was the case was already much more than probable, but so lately as 1835 there were to be found writers on science, such as Comte, who denied that it could ever be proved. But a still more impressive illustration of the unity of Nature is furnished by the luminiferous ether, when considered in connection with the discovery of the correlation of forces. The fathomless abysses of space can no longer be talked of as empty; they are filled with a wonderful substance, unlike any of the forms of matter which we can weigh and measure. A cosmic jelly almost infinitely hard and elastic, it offers at the same time no appreciable resistance to the movements of the heavenly bodies. It is so sensitive that a shock in any part of it causes a "tremour which is felt on the surface of countless worlds." Radiating in every direction, from millions of centric points, run shivers of undulation manifested in endless metamorphosis as heat, or light, or actinism, as magnetism or electricity. Crossing one another in every imaginable way, as if all space were crowded with a mesh-work of nerve-threads, these motions go on forever in a harmony that nothing disturbs. Thus every part of the universe shares in the life of all the other parts, as when in the solar atmosphere, pulsating at its temperature of a million degrees Fahrenheit, a slight breeze instantly sways the needles in every compass-box on the face of the earth.

Still further striking confirmation is found in the marvellous disclosures of spectrum analysis. To whatever part of the heavens we turn the telescope, armed with this new addition to our senses, we find the same chemical elements with which the present century has made us familiar upon the surface of the earth. From the distant worlds of Arcturus and the Pleiades, whence the swift ray of light takes many years to reach us, it brings the story of the hydrogen and oxygen, the vapour of iron or sodium, which set it in motion. Thus in all parts of the universe that have fallen within our ken we find a unity of chemical composition. NebulÆ, stars, and planets are all made of the same materials, and on every side we behold them in different stages of development, worlds in the making: here an irregular nebula such as our solar system once was, there a nebula whose rotation has at length wrought it into spheroidal form; here and there stars of varied colours marking different eras in chemical evolution; now planets still partly incandescent like Saturn and Jupiter, then planets like Mars and the earth, with cool atmospheres and solid continents and vast oceans of water; and lastly such bodies as the moon, vapourless, rigid, and cold in death.

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.

By what name, then, shall we call this animating principle of the universe, this eternal source of phenomena? Using the ordinary language of physics, we have just been calling it Force, but such a term in no wise enlightens us. Taken by itself it is meaningless; it acquires its meaning only from the relations in which it is used. It is a mere symbol, like the algebraic expression which stands for a curve. Of what, then, is it the symbol?

The words which we use are so enwrapped in atmospheres of subtle associations that they are liable to sway the direction of our thoughts in ways of which we are often unconscious. It is highly desirable that physics should have a word as thoroughly abstract, as utterly emptied of all connotations of personality, as possible, so that it may be used like a mathematical symbol. Such a word is Force. But what we are now dealing with is by no means a scientific abstraction. It is the most concrete and solid of realities, the one Reality which underlies all appearances, and from the presence of which we can never escape. Suppose, then, that we translate our abstract terminology into something that is more concrete. Instead of the force which persists, let us speak of the Power which is always and everywhere manifested in phenomena. Our question, then, becomes, What is this infinite and eternal Power like? What kind of language shall we use in describing it? Can we regard it as in any wise "material," or can we speak of its universal and ceaseless activity as in any wise the working of a "blind necessity"? For here, at length, we have penetrated to the innermost kernel of the problem; and upon the answer must depend our mental attitude toward the mystery of existence.

The answer is that we cannot regard the infinite and eternal Power as in any wise "material," nor can we attribute its workings to "blind necessity." The eternal source of phenomena is the source of what we see and hear and touch; it is the source of what we call matter, but it cannot itself be material. Matter is but the generalized name we give to those modifications which we refer immediately to an unknown something outside of ourselves. It was long ago shown that all the qualities of matter are what the mind makes them, and have no existence as such apart from the mind. In the deepest sense all that we really know is mind, and as Clifford would say, what we call the material universe is simply an imperfect picture in our minds of a real universe of mind-stuff.[22] Our own mind we know directly; our neighbour's mind we know by inference; that which is external to both is a Power hidden from sense, which causes states of consciousness that are similar in both. Such states of consciousness we call material qualities, and matter is nothing but the sum of such qualities. To speak of the hidden Power itself as "material" is therefore not merely to state what is untrue,—it is to talk nonsense. We are bound to conceive of the Eternal Reality in terms of the only reality that we know, or else refrain from conceiving it under any form whatever. But the latter alternative is clearly impossible.[23] We might as well try to escape from the air in which we breathe as to expel from consciousness the Power which is manifested throughout what we call the material universe. But the only conclusion we can consistently hold is that this is the very same power "which in ourselves wells up under the form of consciousness."

In the nature-worship of primitive men, beneath all the crudities of thought by which it was overlaid and obscured, there was thus after all an essential germ of truth which modern philosophy is constrained to recognize and reiterate. As the unity of Nature has come to be demonstrated, innumerable finite powers, once conceived as psychical and deified, have been generalized into a single infinite Power that is still thought of as psychical. From the crudest polytheism we have thus, by a slow evolution, arrived at pure monotheism,—the recognition of the eternal God indwelling in the universe, in whom we live and move and have our being.

But in thus conceiving of God as psychical, as a Being with whom the human soul in the deepest sense owns kinship, we must beware of too carelessly ascribing to Him those specialized psychical attributes characteristic of humanity, which one and all imply limitation and weakness. We must not forget the warning of the prophet Isaiah: "My thoughts are not your thoughts, neither are your ways my ways, saith the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." Omniscience, for example, has been ascribed to God in every system of theism; yet the psychical nature to which all events, past, present, and future, can be always simultaneously present is clearly as far removed from the limited and serial psychical nature of Man as the heavens are higher than the earth. We are not so presumptuous, therefore, as to attempt, with some theologians of the anthropomorphic school, to inquire minutely into the character of the divine decrees and purposes. But our task would be ill-performed were nothing more to be said about that craving after a final cause which we have seen to be an essential element in Man's religious nature. It remains to be shown that there is a reasonableness in the universe, that in the orderly sequence of events there is a meaning which appeals to our human intelligence. Without adopting Paley's method, which has been proved inadequate, we may nevertheless boldly aim at an object like that at which Paley aimed. Caution is needed, since we are dealing with a symbolic conception as to which the very point in question is whether there is any reality that answers to it. The problem is a hard one, but here we suddenly get powerful help from the doctrine of evolution, and especially from that part of it known as the Darwinian theory.