Within recent years the psychologists are doing remarkable work in attacking the problem of the mechanics of mental operations, and already in Europe and America some thirty laboratories have been started for experimental work. The subject is somewhat abstruse for detailed reference here, and it must suffice to say that the psychologist, beginning with observations upon himself, measuring, for example, “the degree of sensibility of his own eye to luminous irritations, or of his own skin to pricking, passes on to like inquiry into the numerical relations between the energy of the stimuli of light, sound, and so forth, and the energy of the sensations which they arouse in the nerve-channels.” An excellent summary, with references to the newest authorities on the subject, is given by Prince Kropotkin in the Nineteenth Century of August, 1896.
All this, to the superficial onlooker, seems rank materialism. But we cannot think without a brain any more than we can see without eyes, and any inquiry into the operation of the organ of thought must run on the same lines as inquiry into the operations of any other organ of the body. And the inquiry leaves us at the point whence we began in so far as any light is thrown on the connection between the molecular vibrations in nerve-tissue and the mental processes of which they are the indispensable accompaniment. Changes take place in some of the thousands of millions of brain-cells in every thought that we think, and in every emotion that we feel, but the nexus remains an impenetrable mystery. Nevertheless, if we may not say that the brain secretes thought as we say that the liver secretes bile, we may also not say that the mind is detachable from the nervous system, and that it is an entity independent of it. Were it this, not only would it stand outside the ordinary conditions of development, but it would also maintain the equilibrium which a dose of narcotics or of alcohol, or which starvation and gorging alike rapidly upset.
In his posthumous essay On the Immortality of the Soul, Hume says: “Matter and spirit are at bottom equally unknown, and we cannot determine what qualities inhere in the one or in the other.” That is the conclusion to which the wisest come. And in the ultimate correlation of the physical and psychical lies the hope of arrival at that terminus of unity which was the dream of the ancient Greeks, and to which all inquiry makes approach. How, in these matters, philosophy is at one, is again seen in Huxley’s admission that “in respect of the great problems of philosophy, the post-Darwinian generation is, in one sense, exactly where the præ-Darwinian generations were. They remain insoluble. But the present generation has the advantage of being better provided with the means of freeing itself from the tyranny of certain sham solutions.”
Science explains, and, in explaining, dissipates the pseudo-mysteries by which man, in his myth-making stage, when conception of the order of the universe was yet unborn, accounted for everything. But she may borrow the Apostle’s words, “Behold! I show you a mystery,” and give to them a profounder meaning as she confesses that the origin and ultimate destiny of matter and motion; the causes which determine the behaviour of atoms, whether they are arranged in the lovely and varying forms which mark their crystals, or whether they are quivering with the life which is common to the amœba and the man; the conversion of the inorganic into the organic by the green plant, and the relation between nerve-changes and consciousness; are all impenetrable mysteries.
In his speech on the commemoration of the jubilee of his Professorship in the University of Glasgow last year, Lord Kelvin said, “I know no more of electric and magnetic force, or of the relation between ether, electricity, and ponderable matter, or of chemical affinity than I knew and tried to teach my students of natural philosophy fifty years ago in my first session as professor.”
This recognition of limitations will content those who seek not “after a sign”. For others, that search will continue to have encouragement not only from the theologian, but from the pseudo-scientific who have travelled some distance with the Pioneers of Evolution, but who refuse to follow them further. In each of these there is present the “theological bias” whose varied forms are skilfully analyzed by Mr. Spencer in his chapter under that heading in the Study of Sociology. This explains the attitude of various groups which are severally represented by Mr. St. George Mivart, and the late Dr. W. B. Carpenter; by Professor Sir Geo. G. Stokes, and Mr. Alfred Russel Wallace. The first-named is a Roman Catholic; the second was a Unitarian; the third is an orthodox Churchman, and the fourth, as already seen, is a Spiritualist. In his Genesis of Species, Mr. Mivart contends that “man’s body was evolved from pre-existing material (symbolised by the term ‘dust of the earth’), and was therefore only derivatively created, i. e., by the operation of secondary laws,” but that “his soul, on the other hand, was created in quite a different way ... by the direct action of the Almighty (symbolised by the term breathing),” p. 325. In his Mental Physiology, Dr. Carpenter postulates an Ego or Will which presides over, without sharing in, the causally determined action of the other mental functions and their correlated bodily processes; “an entity which does not depend for its existence on any play of physical or vital forces, but which makes these forces subservient to its determinations” (p. 27). Professor Mivart actually cites St. Augustine and Cardinal Newman as authorities in support of his theory of the special creation of the soul. He might with equal effect subpœna Dr. Joseph Parker or General Booth as authorities. Dr. Carpenter argued as became a good Unitarian. In his Gifford Lectures on Natural Theology, Professor Stokes asserts, drawing “on sources of information which lie beyond man’s natural powers,” in other words, appealing to the Bible, that God made man immortal and upright, and endowed him with freedom of the will. As, without the exercise of this, man would have been as a mere automaton, he was exposed to the temptation of the devil, and fell. Thereby he became “subject to death like the lower animals,” and by the “natural effect of heredity,” transmitted the taint of sin to his offspring. The eternal life thus forfeited was restored by the voluntary sacrifice of Christ, but can be secured only to those who have faith in him. This doctrine, which is no novel one, is known as “conditional immortality.” Professor Stokes attaches “no value to the belief in a future life by metaphysical arguments founded on the supposed nature of the soul itself,” and he admits that the purely psychic theory which would discard the body altogether in regard to the process of thought is beset by very great difficulties. So he once more has recourse to “sources of information which lie beyond man’s natural powers.” Following up certain distinctions between “soul” and “spirit” drawn by the Apostle Paul in his tripartite division of man, Professor Stokes, somewhat in keeping with Dr. Carpenter, assumes an “Ego, which, on the one hand, is not to be identified with thought, which may exist while thought is in abeyance, and which may, with the future body of which the Christian religion speaks, be the medium of continuity of thought.... What the nature of this body might be we do not know; but we are pretty distinctly informed that it would be something very different from that of our present body, very different in its properties and functions, and yet no less our own than our present body.” “Words, words, words,” as Hamlet says.
Reference has been made in some fulness to Mr. Wallace’s limitations of the theory of natural selection in the case of man’s mental faculties. We must now pursue this somewhat in detail, reminding the reader of Mr. Wallace’s admission that, “provisionally, the laws of variation and natural selection ... may have brought about, first, that perfection of bodily structure in which man is so far above all other animals, and, in co-ordination with it, the larger and more developed brain by means of which he has been able to subject the whole animal and vegetable kingdoms to his service.” But, although Mr. Wallace rejects the theory of man’s special creation as “being entirely unsupported by facts, as well as in the highest degree improbable,” he contends that it does not necessarily follow that “his mental nature, even though developed pari passu with his physical structure, has been developed by the same agencies.” Then, by the introduction of a physical analogy which is no analogy at all, he suggests that the agent by which man was upraised into a kingdom apart bears like relation to natural selection as the glacial epoch bears to the ordinary agents of denudation and other changes in producing new effects which, though continuous with preceding effects, were not due to the same causes.
Applying this “argument” (drawn from natural causes), as Mr. Wallace names it, “to the case of man’s intellectual and moral nature,” he contends that such special faculties as the mathematical, musical, and artistic (is this faculty to be denied the nest-decorating bower bird?), and the high moral qualities which have given the martyr his constancy, the patriot his devotion, and the philanthropist his unselfishness, are due to a “spiritual essence or nature, superadded to the animal nature of man.” We are not told at what stage in man’s development this was inserted; whether, once and for all, in “primitive” man, with potentiality of transmission through Palæolithic folk to all succeeding generations; or whether there is special infusion of a “spiritual essence” into every human being at birth.
Any perplexity that might arise at the line thus taken by Mr. Wallace vanishes before the fact, already enlarged upon, that the author of the Malay Archipelago and Island Life has written a book on Miracles and Modern Spiritualism in defence of both. The explanation lies in that duality of mind which, in one compartment, ranks Mr. Wallace foremost among naturalists, and, in the other compartment, places him among the most credulous of Spiritualists.
Despite this, Mr. Wallace has claims to a respectful hearing and to serious reply. Fortunately, he would appear to furnish the refutation to his own argument in the following paragraph from his delightful Contributions to the Theory of Natural Selection: