II. The combinations of elements which are peculiar to organisms, and which are responsible for their vital phenomena, are compound protoplasmic substances, of the group of albuminates.
III. Organic life itself is a chemico-physical process, based on the metabolism (or interchange of material) of these albuminates.
IV. The only element which is capable of building up these compound albuminates, in combination with other elements (oxygen, hydrogen, nitrogen, and sulphur), is carbon.
V. These protoplasmic compounds of carbon are distinguished from most other chemical combinations by their very intricate molecular structure, their instability, and their jelly-like consistency.
On the basis of these five fundamental facts the following “carbon-theory” was erected thirty-three years ago: “The peculiar chemico-physical properties of carbon—especially the fluidity and the facility of decomposition of the most elaborate albuminoid compounds of carbon—are the sole and the mechanical causes of the specific phenomena of movement, which distinguish organic from inorganic substances, and which are called life, in the usual sense of the word” (see The Natural History of Creation). Although this “carbon-theory” is warmly disputed in some quarters, no better monistic theory has yet appeared to replace it. We have now a much better and more thorough knowledge of the physiological relations of cell-life, and of the chemistry and physics of the living protoplasm, than we had thirty-three years ago, and so it is possible to make a more confident and effective defence of the carbon-theory.
The old idea of spontaneous generation is now taken in many different senses. It is owing to this indistinctness of the idea, and its application to so many different hypotheses, that the problem is one of the most contentious and confused of the science of the day. I restrict the idea of spontaneous generation—also called abiogenesis or archigony—to the first development of living protoplasm out of inorganic carbonates, and distinguish two phases in this “beginning of biogenesis”: (1) autogony, or the rise of the simplest protoplasmic substances in a formative fluid, and (2) plasmogony, the differentiation of individual primitive organisms out of these protoplasmic compounds, in the form of monera. I have treated this important, though difficult, problem so exhaustively in the fifteenth chapter of my Natural History of Creation that I may content myself here with referring to it. There is also a very searching and severely scientific inquiry into it in my General Morphology (1866). Naegeli has also treated the hypothesis in quite the same sense in his mechanico-physiological theory of descent (1884), and has represented it to be an indispensable thesis in any natural theory of evolution. I entirely agree with his assertion that “to reject abiogenesis is to admit a miracle.”
The hypothesis of spontaneous generation and the allied carbon-theory are of great importance in deciding the long-standing conflict between the teleological (dualistic) and the mechanical (monistic) interpretation of phenomena. Since Darwin gave us the key to the monistic explanation of organization in his theory of selection forty years ago, it has become possible for us to trace the splendid variety of orderly tendencies of the organic world to mechanical, natural causes, just as we could formerly in the inorganic world alone. Hence the supernatural and telic forces, to which the scientist had had recourse, have been rendered superfluous. Modern metaphysics, however, continues to regard the latter as indispensable and the former as inadequate.
No philosopher has done more than Immanuel Kant in defining the profound distinction between efficient and final causes, with relation to the interpretation of the whole cosmos. In his well-known earlier work on The General Natural History and Theory of the Heavens he made a bold attempt “to treat the constitution and the mechanical origin of the entire fabric of the universe according to Newtonian laws.” This “cosmological nebular theory” was based entirely on the mechanical phenomena of gravitation. It was expanded and mathematically established later on by Laplace. When the famous French astronomer was asked by Napoleon I. where God, the creator and sustainer of all things, came in in his system, he clearly and honestly replied: “Sire, I have managed without that hypothesis.” That indicated the atheistic character which this mechanical cosmogony shares with all the other inorganic sciences. This is the more noteworthy because the theory of Kant and Laplace is now almost universally accepted; every attempt to supersede it has failed. When atheism is denounced as a grave reproach, as it so often is, it is well to remember that the reproach extends to the whole of modern science, in so far as it gives a purely mechanical interpretation of the inorganic world.
Mechanicism (in the Kantian sense) alone can give us a true explanation of natural phenomena, for it traces them to their real efficient causes, to blind and unconscious agencies, which are determined in their action only by the material constitution of the bodies we are investigating. Kant himself emphatically affirms that “there can be no science without this mechanicism of nature,” and that the capacity of human reason to give a mechanical interpretation of phenomena is unlimited. But when he came subsequently to give an elucidation of the complex phenomena of organic nature in his critique of the teleological system, he declared that these mechanical causes were inadequate; that in this we must call final causes to our assistance. It is true, he said, that even here we must recognize the theoretical faculty of the mind to give a mechanical interpretation, but its actual competence to do so is restricted. He grants it this capacity to some extent; but for the majority of the vital processes (and especially for man’s psychic activity) he thinks we are bound to postulate final causes. The remarkable §79 of the critique of judgment bears the characteristic heading: “On the Necessity for the Subordination of the Mechanical Principle to the Teleological in the Explanation of a Thing as a Natural End.” It seemed to Kant so impossible to explain the orderly processes in the living organism without postulating supernatural final causes (that is, a purposive creative force) that he said: “It is quite certain that we cannot even satisfactorily understand, much less elucidate, the nature of an organism and its internal faculty on purely mechanical natural principles; it is so certain, indeed, that we may confidently say, ‘It is absurd for a man to conceive the idea even that some day a Newton will arise who can explain the origin of a single blade of grass by natural laws which are uncontrolled by design’—such a hope is entirely forbidden us.” Seventy years afterwards this impossible “Newton of the organic world” appeared in the person of Charles Darwin, and achieved the great task that Kant had deemed impracticable.
Since Newton (1682) formulated the law of gravitation, and Kant (1755) established “the constitution and mechanical origin of the entire fabric of the world on Newtonian laws,” and Laplace (1796) provided a mathematical foundation for this law of cosmic mechanicism, the whole of the inorganic sciences have become purely mechanical, and at the same time purely atheistic. Astronomy, cosmogony, geology, meteorology, and inorganic physics and chemistry are now absolutely ruled by mechanical laws on a mathematical foundation. The idea of “design” has wholly disappeared from this vast province of science. At the close of the nineteenth century, now that this monistic view has fought its way to general recognition, no scientist ever asks seriously of the “purpose” of any single phenomenon in the whole of this great field. Is any astronomer likely to inquire seriously to-day into the purpose of planetary motion, or a mineralogist to seek design in the structure of a crystal? Does the physicist investigate the purpose of electric force, or the chemist that of atomic weight? We may confidently answer in the negative—certainly not, in the sense that God, or a purposive natural force, had at some time created these fundamental laws of the mechanism of the universe with a definite design, and causes them to work daily in accordance with his rational will. The anthropomorphic notion of a deliberate architect and ruler of the world has gone forever from this field; the “eternal, iron laws of nature” have taken his place.