The preceding remarks are intended to suggest that the theory of evolution, combined with the quite recent and very startling advances in physical science, so far from making the universe around us more intelligible as a self-sustaining and self-existent whole, has really rendered it less so, by showing that it is infinitely more complex than we had formerly supposed; and further, that matter itself, instead of being, as was once believed, a comparatively simple thing, eternal and indestructible, is in all its various forms subject to decay and disintegration. We now see that the only thing known to us that we can conceive as having unending existence is mind itself; and, just as Darwin’s theory of Natural Selection has opened up to us an infinite field of study and admiration in the forms and colours and mutual relations of the various species of animals and plants, so does modern science open up to us new and unfathomable depths in the inner structure of matter and of the cosmos, and thus compels us more and more to recognise a mental rather than a mere physical substratum to account for its existence.
There is, however, another set of relations which have been hitherto very little studied—those between the organic and the inorganic worlds in their broader aspects. These are now found to be very much more complex and more remarkable than is usually supposed, and they also have an important bearing upon the great problem of the origin and destiny of man. This is a subject which opens up a variety of considerations of extreme interest, showing that the exact adaptations of our earth—and presumably of any other planets—to enable it to sustain organic life, from its first appearance and through its long course of development, is as varied and complex and as much beyond the possibilities of chance coincidences as are any of the individual adaptations of animals and plants to their immediate environment. Most of these latter adaptations have been made known to us by Darwin and his followers, and they have excited the admiration and astonishment of all lovers of Nature. When the antecedent and grander relations of planet to life are studied with equal care, these also will, I believe, excite deeper admiration, still more profound astonishment, because any secondary laws that could have brought them about are less easy to discover, or even to imagine.
Essential Conditions of Life
Before we can form any adequate idea of the nature of a world which shall be able to support and develop organic life, we must consider what are the special conditions that alone render such life possible. We, of course, refer to the whole of the organic world, from the lowest to the highest, not to the few exceptional cases in which life may be possible under conditions that would be fatal to the higher as well as to most of the lower forms.
The Miracle of Human Life
The one striking speciality of the higher animals—and to a less degree of the higher plants—is that of continuous, all-pervading motion, every portion of their substance being in a state of flux: each particle itself moving, growing, living and dying, and being replaced by other particles of the same nature and fulfilling the same functions. To keep up this growth, and to enable every part of the structure to be continually renewed, food is required. This is taken into the stomach of animals in the solid or liquid form, is then decomposed and recomposed, that which is useless or superfluous being thrown off by the intestines, while what is needed for growth is transformed into blood and by a wonderfully intricate system of branching tubes is carried to every part of the body, furnishing nourishment and repair alike to bone and muscle, to all the internal organs and all the outward integuments, and to that marvellously complex nervous system which also permeates every part of the body and is essential to the higher manifestations of life—to the exertion of force, voluntary motion, and, apparently, to thought itself. Add to this the constant influx of air, which at once purifies the blood and supplies animal heat, and is so important that its cessation for a few minutes is usually fatal, and we have a machine so complex in its structure and mode of action that the most elaborate of human machines is but as a grain of sand to a world in comparison.
Basis of Physical Life
Now the very possibility of such a material organism as this depends upon a highly complex form of matter termed protoplasm, which is at once extremely plastic and of extreme instability, and is yet capable of secreting or building up its atoms into such solid and apparently durable forms as bone, horn, and hair, besides the various liquids and semi-solids which build up the organism. This fundamental organic substance consists of only four chemical elements—nitrogen, hydrogen, oxygen and carbon, and almost all animal and vegetable structures and products have the same elemental constitution, though with such widely different characteristics. Four other elements—sulphur, lime, silicon, and phosphorus—also occur in small quantities in organic tissues, to supply special needs; but these are not essential to all forms of life, and are only taken up and utilised by the living protoplasm when required. Protoplasm is undoubtedly the basis of physical life, yet it only exists in, and is produced by, living organisms. The moment such an organism dies, disorganisation and decay set in, and the whole mass becomes gradually changed into more stable compounds, or into its constituent elements. It appears, therefore, that some agency—usually termed “vital force”—must be at work, first to produce this wonderful compound, then to form it into “cells”—the physiological units of all organisms—and afterwards to direct the energies supplied by heat and light so as to build up the excessively complex structures, with all their wonderful powers and potentialities, which we term animals and plants. All this seems to imply not “a force” only, but very many forces, all of which must have some kind of mind in or behind them, to direct these forces to such infinitely varied yet perfectly defined ends.
A Marvel of Every Day
Consider for a moment one of the simplest of these cases. Let us take the minute seed of one of the great tropical fig-trees, and another seed of a strawberry, or of garden cress. Both will be about the same size and shape, and the most acute microscopist would not find any difference in the internal structure that could intelligibly account for the different results when these little grains of protoplasm are exposed to identical conditions. For, even if planted near each other, and exposed to the same amount of heat and moisture, to the very same atmosphere, and the same kind of water, as well as identically the same soil, yet invariably the one will grow into a large tree, the other into a small herb, and in the course of time, still with no change whatever of the physical conditions to which both are exposed, each will produce its peculiar foliage, and flowers, and fruit, very different in all their characters from those of the other. Were this result not so common as to seem to us “natural,” we should call it a miracle; and it is really and essentially as inexplicable as many things which are termed miracles only because they are unfamiliar and inexplicable.