Life processes cease, but chemical and mechanical processes go on forever. Life is as fugitive and uncertain as the bow in the clouds, and, like the bow in the clouds, is confined to a limited range of conditions. Like the bow, also, it is a perpetual creation, a constant becoming, and its source is not in the matter through which it is manifested, though inseparable from it. The material substance of life, like the rain-drops, is in perpetual flux and change; it hangs always on the verge of dissolution and vanishes when the material conditions fail, to be renewed again when they return. We know, do we not? that life is as literally dependent upon the sun as is the rainbow, and equally dependent upon the material elements; but whether the physical conditions sum up the whole truth about it, as they do with the bow, is the insoluble question. Science says "Yes," but our philosophy and our religion say "No." The poets and the prophets say "No," and our hopes and aspirations say "No."
II
Where, then, shall we look for the key to this mysterious thing we call life? Modern biochemistry will not listen to the old notion of a vital force—that is only a metaphysical will-o'-the-wisp that leaves us floundering in the quagmire. If I question the forces about me, what answer do I get? Molecular attraction and repulsion seem to say, "It is not in us; we are as active in the clod as in the flower." The four principal elements—oxygen, nitrogen, hydrogen, and carbon—say, "It is not in us, because we are from all eternity, and life is not; we form only its physical basis." Warmth and moisture say, "It is not in us; we are only its faithful nurses and handmaidens." The sun says: "It is not in me; I shine on dead worlds as well. I but quicken life after it is planted." The stars say, "It is not in us; we have seen life come and go among myriads of worlds for untold ages." No questioning of the heavens above nor of the earth below can reveal to us the secret we are in quest of.
I can fancy brute matter saying to life: "You tarry with me at your peril. You will always be on the firing-line of my blind, contending forces; they will respect you not; you must take your chances amid my flying missiles. My forces go their eternal round without variableness or shadow of turning, and woe to you if you cross their courses. You may bring all your gods with you—gods of love, mercy, gentleness, altruism; but I know them not. Your prayers will fall upon ears of stone, your appealing gesture upon eyes of stone, your cries for mercy upon hearts of stone. I shall be neither your enemy nor your friend. I shall be utterly indifferent to you. My floods will drown you, my winds wreck you, my fires burn you, my quicksands suck you down, and not know what they are doing. My earth is a theatre of storms and cyclones, of avalanches and earthquakes, of lightnings and cloudbursts; wrecks and ruins strew my course. All my elements and forces are at your service; all my fluids and gases and solids; my stars in their courses will fight on your side, if you put and keep yourself in right relations to them. My atoms and electrons will build your houses, my lightning do your errands, my winds sail your ships, on the same terms. You cannot live without my air and my water and my warmth; but each of them is a source of power that will crush or engulf or devour you before it will turn one hair's-breadth from its course. Your trees will be uprooted by my tornadoes, your fair fields will be laid waste by floods or fires; my mountains will fall on your delicate forms and utterly crush and bury them; my glaciers will overspread vast areas and banish or destroy whole tribes and races of your handiwork; the shrinking and wrinkling crust of my earth will fold in its insensate bosom vast forests of your tropical growths, and convert them into black rock, and I will make rock of the myriad forms of minute life with which you plant the seas; through immense geologic ages my relentless, unseeing, unfeeling forces will drive on like the ploughshare that buries every flower and grass-blade and tiny creature in its path. My winds are life-giving breezes to-day, and the besom of destruction to-morrow; my rains will moisten and nourish you one day, and wash you into the gulf the next; my earthquakes will bury your cities as if they were ant-hills. So you must take your chances, but the chances are on your side. I am not all tempest, or flood, or fire, or earthquake. Your career will be a warfare, but you will win more battles than you will lose. But remember, you are nothing to me, while I am everything to you. I have nothing to lose or gain, while you have everything to gain. Without my soils and moisture and warmth, without my carbon and oxygen and nitrogen and hydrogen, you can do or be nothing; without my sunshine you perish; but you have these things on condition of effort and struggle. You have evolution on condition of pain and failure and the hazard of the warring geologic ages. Fate and necessity rule in my realm. When you fail, or are crushed or swallowed by my remorseless forces, do not blame my gods, or your own; there is no blame, there is only the price to be paid: the hazards of invading the closed circle of my unseeing forces."
In California I saw an epitome of the merciless way inorganic Nature deals with life. An old, dried, and hardened asphalt lake near Los Angeles tells a horrible tale of animal suffering and failure. It had been a pit of horrors for long ages; it was Nature concentrated—her wild welter of struggling and devouring forms through the geologic ages made visible and tangible in a small patch of mingled pitch and animal bones. There was nearly as much bone as pitch. The fate of the unlucky flies that alight upon tangle-foot fly-paper in our houses had been the fate of the victims that had perished here. How many wild creatures had turned appealing eyes to the great unheeding void as they felt themselves helpless and sinking in this all-engulfing pitch! In like manner how many human beings in storms and disasters at sea and in flood and fire upon land have turned the same appealing look to the unpitying heavens! There is no power in the world of physical forces, or apart from our own kind, that heeds us or turns aside for us, or bestows one pitying glance upon us. Life has run, and still runs, the gantlet of a long line of hostile forces, and escapes by dint of fleetness of foot, or agility in dodging, or else by toughness of fibre.
Yet here we are; here is love and charity and mercy and intelligence; the fair face of childhood, the beautiful face of youth, the clear, strong face of manhood and womanhood, and the calm, benign face of old age, seen, it is true, as against a background of their opposites, but seeming to indicate something above chance and change at the heart of Nature. Here is life in the midst of death; but death forever playing into the hands of life; here is the organic in the midst of the inorganic, at strife with it, hourly crushed by it, yet sustained and kept going by its aid.
III
Vitality is only a word, but it marks a class of phenomena in nature that stands apart from all merely mechanical manifestations in the universe. The cosmos is a vast machine, but in this machine—this tremendous complex of physical forces—there appears, at least on this earth, in the course of its evolution, this something, or this peculiar manifestation of energy, that we call vital. Apparently it is a transient phase of activity in matter, which, unlike other chemical and physical activities, has its beginning and its ending, and out of which have arisen all the myriad forms of terrestrial life. The merely material forces, blind and haphazard from the first, did not arise in matter; they are inseparable from it; they are as eternal as matter itself; but the activities called vital arose in time and place, and must eventually disappear as they arose, while the career of the inorganic elements goes on as if life had never visited the sphere. Was it, or is it, a visitation—something ab extra that implies super-mundane, or supernatural, powers?
Added to this wonder is the fact that the vital order has gone on unfolding through the geologic ages, mounting from form to form, or from order to order, becoming more and more complex, passing from the emphasis of size of body, to the emphasis of size of brain, and finally from instinct and reflex activities to free volition, and the reason and consciousness of man; while the purely physical and chemical forces remain where they began. There has been endless change among them, endless shifting of the balance of power, but always the tendency to a dead equilibrium, while the genius of the organic forces has been in the power to disturb the equilibrium and to ride into port on the crest of the wave it has created, or to hang forever between the stable and the unstable.
So there we are, confronted by two apparently contrary truths. It is to me unthinkable that the vital order is not as truly rooted in the constitution of things as are the mechanical and chemical orders; and yet, here we are face to face with its limited, fugitive, or transitional character. It comes and goes like the dews of the morning; it has all the features of an exceptional, unexpected, extraordinary occurrence—of miracle, if you will; but if the light which physical science turns on the universe is not a delusion, if the habit of mind which it begets is not a false one, then life belongs to the same category of things as do day and night, rain and sun, rest and motion. Who shall reconcile these contradictions?