If the fundamental proposition of evolution is true, namely, that the entire world, animate and inanimate, is the result of the mutual interaction, according to definite laws, of forces possessed by the molecules which made up the primitive nebulosity of the universe; then it is no less certain that the present actual world reposed potentially in the cosmic vapour, and that an intelligence, if great enough, could from his knowledge of the properties of the molecules of that vapour have predicted the state of the fauna in Great Britain in 1888 with as much certitude as we say what will happen to the vapour of our breath on a cold day in winter.
Now, if the principle of evolution be accepted, the truth of Huxley's statement appears to be self-evident. It may be that no intelligence capable of making such a calculation will ever exist, but the abstract possibility remains. Professor Thomson calls it "a very strong and confident statement," which illustrates the need for philosophical criticism. His criticism of Huxley's statement is based on two grounds. These are: (1) "No complete physico-chemical description has ever been given of any distinctively vital activity; and (2) the physical description of things cannot cover biological phenomena, nor can the biological description cover mental and moral phenomena." There is, he says,
The physical order of nature—the inorganic world—where mechanism reigns supreme. (2) There is the vital order of nature—the world of organisms—where mechanism proves insufficient. (3) There is the physical order of nature—the world of mind—where mechanism is irrelevant. Thus there are three fundamental sciences—Physics, Biology, and Psychology—each with characteristic questions, categories and formulæ.
Now, however earnestly Huxley's statement calls for criticism, it is clear to us that nothing useful in that direction is offered by Prof. Thomson. It is quite plain that the abstract possibility of such a calculation as that named by Huxley can never be ruled out by science, since such a conception lies at the root of all scientific thinking. After all, want of knowledge only proves—want of knowledge; and Sir Oliver Lodge would warn Prof. Thomson of the extreme danger of resting an argument on the ignorance of science at any particular time.[4]
I note this statement of Professor Thomson's chiefly because it illustrates a very common method of dealing with the mechanistic or non-theistic view of the universe. In this matter Professor Thomson may claim the companionship of Sir Oliver Lodge, who says, "Materialism is appropriate to the material world, not as a philosophy, but as a working creed, as a proximate, an immediate formula for guiding research. Everything beyond that belongs to another region, and must be reached by other methods. To explain the psychical in terms of physics and chemistry is simply impossible.... The extreme school of biologists ... ought to say, if they were consistent, there is nothing but physics and chemistry at work anywhere." With both these writers there is the common assumption that the mechanist assumes there is a physical and chemical explanation of all phenomena. And the assumption is false. There is a story of a well-known lecturer on physiology who commenced an address on the stomach by remarking that that organ had been called this, that, and the other, but the one thing he wished his students to bear in mind was that it was a stomach. So the mechanist, while firmly believing that there is an ascending unity in all natural phenomena, is never silly enough to deny that living things are alive, or that thinking beings think.
But unless Professor Thomson does impute this to the mechanist, we quite fail to see the relevance his assertion that there are three departments, physics, biology, and psychology, each with its characteristic questions, categories, and formulæ. Of course, there are, and equally, of course, physical laws will not cover biological facts; nor will biological laws cover psychological ones. This is not due to any occult cause, but to the simple fact that as each group of phenomena has its characteristic features, each set of laws are framed to cover the phenomena presented by that group. Otherwise there would be no need of these special laws. It is astonishing how paralysing is the effect of the theistic obsession on the minds of even scientific men, since it leads them to ignore what is really a basic consideration in scientific method.
Perhaps a word or two more on this topic is advisable. If it is permissible to arrange natural phenomena in a serial order, we may place them in succession as physical, chemical, biological, and psychological. But these names represent no more than descriptions of certain features that are to the group common, otherwise the grouping would be useless and impossible. And it is part of the business of science to frame "laws"—descriptions—of phenomena such as will enable us to express their characteristic features in a brief formula. It is, therefore, quite true to say that you cannot express vital phenomena in terms of physics or chemistry. And no materialist who took the trouble to understand materialism, instead of taking a statement of what it is from an anti-materialist, ever thought otherwise. Each specific group of phenomena can only be covered by laws that belong to that group, and which were framed for that express purpose. A psychological fact can no more be expressed in terms of chemistry than a physical fact can be expressed in terms of biology. These truths are as plain to the mechanist as they are to the vitalist. Mental life, the scientific categories, are real to all; the only question at issue is that of their origin.
To explain is to make intelligible, and in that sense all scientific explanation consists in the establishing of equivalents. When we say that A, B, C are the factors of D, we have asserted D is the equivalent of A, B, C—plus, of course, all that results from the combination of the factors. When we say that we have explained the formation of water by showing it to be the product of H.2.O. we have shown that whether we say "water" or use the chemical formula we are making identical statements. If we are working out a problem in dynamics we meet with exactly the same principle. We must prove that the resultant accounts for all the forces in operation at the time. Now, all that the mechanist claims is that it is extremely probable that one day the scientist will be able to work out the exact physico-chemical conditions that are the equivalents of biological phenomena, and, in turn, the physico-chemical-biological conditions that are the equivalents of psychological phenomena. Very considerable progress has already been made in this direction, and, as Sir Oliver Lodge says, there are probably very few scientific men who would deny the likelihood of this being done.
But this does not deny the existence of differences between these groups of phenomena; neither does it assert that we can describe the characteristic features of one group in terms that belong to another group. Once a group of phenomena, biological, or chemical is there, we must have special formulæ to describe them, otherwise there would be no need for these divisions. It is admitted that the earth was at one time destitute of life; it is also admitted that there are forms of life destitute of those features which we call mind. And, whatever be their mode of origin, once introduced they must be dealt with in special terms. Psychological facts must be expressed in terms of psychology, biological facts in terms of biology, and chemical facts in terms of chemistry. You may give the chemical and physical equivalent of a sunset. That is one aspect. You may also give the psychological explanation of the emotion of man on beholding it. That is another aspect. But you cannot express the psychological fact in terms of chemistry because it belongs to quite another category. A psychological fact, as such, is ultimate. So is a chemical or a biological fact. If by analysis you reduce the psychological fact to its chemical and biological equivalents, its character as a psychological fact is destroyed. That is the product of the synthesis, and to seek in analysis for what only exists in synthesis, is surely to altogether misunderstand the spirit of scientific method. The curious thing is that a mere layman should have to correct men of science on this matter.