We have not yet reached the heart of Mr. Darwin’s theory. The main idea of his system lies in the word “natural.” He uses that word in two senses: first, as antithetical to the word artificial. Men can produce very marked varieties as to structure and habits of animals. This is exemplified in the production of the different breeds of horses, cattle, sheep, and dogs; and specially, as Mr. Darwin seems to think, in the case of pigeons. Of these, he says, “The diversity of breeds is something astonishing.” Some have long, and some very short bills; some have large feet, some small; some long necks, others long wings and tails, while others have singularly short tails; some have thirty, and even forty, tail-feathers, instead of the normal number of twelve or fourteen. They differ as much in instinct as they do in form. Some are carriers, some pouters, some tumblers, some trumpeters; and yet all are descendants of the Rock Pigeon which is still extant. If, then, he argues, man, in a comparatively short time, has by artificial selection produced all these varieties, what might be accomplished on the boundless scale of nature, during the measureless ages of the geologic periods.
Secondly, he uses the word natural as antithetical to supernatural. Natural selection is a selection made by natural laws, working without intention and design. It is, therefore, opposed not only to artificial selection, which is made by the wisdom and skill of man to accomplish a given purpose, but also to supernatural selection, which means either a selection originally intended by a power higher than nature; or which is carried out by such power. In using the expression Natural Selection, Mr. Darwin intends to exclude design, or final causes. All the changes in structure, instinct, or intelligence, in the plants or animals, including man, descended from the primordial germ, or animalcule, have been brought about by unintelligent physical causes. On this point he leaves us in no doubt. He defines nature to be “the aggregate action and product of natural laws; and laws are the sequence of events as ascertained by us.” It had been objected that he often uses teleological language, speaking of purpose, intention, contrivance, adaptation, etc. In answer to this objection, he says: “It has been said, that I speak of natural selection as a power or deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planet?” He admits that in the literal sense of the words, natural selection is a false term; but “who ever objected to chemists, speaking of the elective affinities of various elements?—and yet an acid cannot strictly be said to elect the base with which it in preference combines.” (p. 93) We have here an affirmation and a negation. It is affirmed that natural selection is the operation of natural laws, analogous to the action of gravitation and of chemical affinities. It is denied that it is a process originally designed, or guided by intelligence, such as the activity which foresees an end and consciously selects and controls the means of its accomplishment. Artificial selection, then, is an intelligent process; natural selection is not.
There are in the animal and vegetable worlds innumerable instances of at least apparent contrivance, which have excited the admiration of men in all ages. There are three ways of accounting for them. The first is the Scriptural doctrine, namely, that God is a Spirit, a personal, self-conscious, intelligent agent; that He is infinite, eternal, and unchangeable in his being and perfections; that He is ever present; that this presence is a presence of knowledge and power. In the external world there is always and everywhere indisputable evidence of the activity of two kinds of force: the one physical, the other mental. The physical belongs to matter, and is due to the properties with which it has been endowed; the other is the everywhere present and ever acting mind of God. To the latter are to be referred all the manifestations of design in nature, and the ordering of events in Providence. This doctrine does not ignore the efficiency of second causes; it simply asserts that God over-rules and controls them. Thus the Psalmist says, “I am fearfully and wonderfully made… My substance was not hid from thee, when I was made in secret, and curiously wrought (or embroidered) in the lower parts of the earth. Thine eyes did see my substance yet being imperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there were none of them.” “He who fashioned the eye, shall not He see? He that formed the ear shall not He hear?” “God makes the grass to grow, and herbs for the children of men.” He sends rain, frost, and snow. He controls the winds and the waves. He determines the casting of the lot, the flight of an arrow, and the falling of a sparrow. This universal and constant control of God is not only one of the most patent and pervading doctrines of the Bible, but it is one of the fundamental principles of even natural religion.