EVOLUTION UNIVERSAL
The Starting-point—Inorganic Evolution—What Spencer tried to do—Summary of his Evolutionism—Notes and Queries—The Origin of Life—Evolution of Mind—Ascent of Man—The Scientific Position
Every attempt to describe how our world has come to be as it is must begin somewhere. It must postulate an initial state of Being from which to start any particular chapter in the story of Becoming. How the simplest conceivable raw material began—if it ever began—the evolutionist cannot tell.
The Starting-point.—Spencer began as far back as his scientific imagination could take him—with "formless diffused matter." With this to start with, he utilised the "Nebular Hypothesis" of Laplace, which showed how the planetary system may have arisen by the diffused matter becoming aggregated through the force of attraction into different centres. This theory has been corroborated and improved by subsequent researches in thermodynamics and spectroscopy, and in a modified form it is very generally accepted. The researches of Sir Norman Lockyer on "Inorganic Evolution" (1900) and of M. Faye (Sur l'origine du monde, 2nd. ed., Paris 1885) have strengthened and broadened the foundation of Spencer's Evolutionism; many inquiries point to the idea that matter has a homogeneous constitution; and the recent revolutionary discoveries centred in "radio-activity" have given new life to the view that the eighty odd elements of the chemist have had a long history behind them, and have evolved from simple homogeneous units. The alchemists' dream seems to be coming true, for we hear whispers of the transmutation of elements. "It may be true," as Prof. R. K. Duncan says in his New Knowledge (1905) "that all bodily existence is but the manifestation of units of negative electricity lying embosomed in an omnipresent ether of which these units are, probably, a conditioned part."
Inorganic Evolution.—We cannot follow this fascinating new story of inorganic evolution, but we wish to point out that the progress of science since Spencer wrote his First Principles has tended to justify him in beginning with formless diffused homogeneous matter. Were that work being written to-day, it would have to be entirely recast. It would probably begin (as Prof. Duncan sketches) with units of negative electricity, assuming motion and carrying with them bound portions of the ether in which they are bathed, becoming corpuscles endowed with the primary qualities of matter superimposed upon those of electricity. "Corpuscles congregating into groups or various configurations constitute essentially the atoms of the chemical elements, locking up in these configurations super-terrific energies, and leaving but "a slight residual effect" as chemical affinity or gravitation with which we attempt to carry on the work of the world. These atoms, congregating in their turn as nebulæ and under the slight residual force of gravitation condense into blazing suns. The suns decay in their temperature and become ever more and more complex in their constitution as the atoms lock themselves into multiple forms. We then see these multiple atoms developing up into the molecules of matter to form a world. We see the molecules growing ever more and more complex as the world grows colder until we attain to organic compounds. We see these organic compounds united to form living beings and we see these living beings developing into countless forms, and, after æons of time, evolving into a dominant race which is Us" (The New Knowledge, pp. 252-3). Of course there is both imagination and faith in Prof. Duncan's "We see," but no one at all aware of recent advances will doubt that the scientific cosmogony is evolving rapidly, and that its movement is towards a fuller revelation of the Unity of Nature.
What Spencer tried to do.—Spencer's aim was to show that "our harmonious Universe once existed potentially as formless diffused matter, and has slowly grown into its present organised state." He sought to account for its growing "in terms of Matter, Motion, and Force." Of course he was careful to explain that "the interpretation of all phenomena in terms of Matter, Motion, and Force, is nothing more than the reduction of our complex symbols of thought, to the simplest symbols; and when the equation has been brought to its lowest terms the symbols remain symbols still." His common denominator for all phenomena was "Matter, Motion, and Force," but he also recognised a greatest common measure—"the unknown Cause co-extensive with all orders of phenomena," "the unknown Reality which underlies all things," "a Power of which the nature remains for ever inconceivable," and of which phenomena are merely the manifestations. But while he was technically an abstract Monist, he was practically a "mechanist," believing that it was feasible to redescribe all evolution in terms of mechanical categories. The scientific ideal to which he looked forward is expressed in the sentence: "Given the Persistence of Force, and given the various derivative laws of Force, and there has to be shown not only how the actual existences of the inorganic world necessarily exhibit the traits they do, but how there necessarily result the more numerous and involved traits exhibited by organic and super-organic existences—how an organism is evolved, what is the genesis of human intelligence, whence social progress arises?" (First Principles, p. 555). He looked forward to a unification of knowledge, to "one science, which has for its object-matter the continuous transformation which the universe undergoes." "Evolution being a universal process, one and continuous throughout all forms of existence, there can be no break, no change from one group of concrete phenomena to another without a bridge of intermediate phenomena."
Summary of Spencer's Evolutionism.—Spencer drew up the following summary for publication in Appleton's American Cyclopædia.[10]
[10] Quoted from Prof. W. H. Hudson's Introduction to the Philosophy of Herbert Spencer.
1. Throughout the universe, in general, and in detail, there is an unceasing redistribution of matter and motion.
2. This redistribution constitutes evolution where there is a predominant integration of matter and dissipation of motion, and constitutes dissolution where there is a predominant absorption of motion and disintegration of matter.
3. Evolution is simple when the process of integration, or the formation of a coherent aggregate, proceeds uncomplicated by other processes.
4. Evolution is compound when, along with this primary change from an incoherent to a coherent state, there go on secondary changes, due to differences in the circumstances of the different parts of the aggregate.
5. These secondary changes constitute a transformation of the homogeneous into the heterogeneous—a transformation which, like the first, is exhibited in the universe as a whole and in all (or nearly all) its details—in the aggregate of stars and nebulæ; in the planetary system; in the earth as an inorganic mass; in each organism, vegetal or animal (von Baer's law); in the aggregate of organisms throughout geologic time; in the mind; in society; in all products of social activity.
6. The process of integration, acting locally as well as generally, combines with the process of differentiation to render this change, not simply from homogeneity to heterogeneity, but from an indefinite homogeneity to a definite heterogeneity; and this trait of increasing definiteness, which accompanies the trait of increasing heterogeneity, is, like it, exhibited in the totality of things, and in all its divisions and sub-divisions down to the minutest.
7. Along with this redistribution of the matter composing any evolving aggregate there goes on a redistribution of the retained motion of its components in relation to one another; this also becomes, step by step, more definitely heterogeneous.
8. In the absence of a homogeneity that is infinite and absolute, this redistribution, of which evolution is one phase, is inevitable. The causes which necessitate it are:—
9. The instability of the homogeneous, which is consequent upon the different exposures of the different parts of any limited aggregate to incident forces. The transformations hence resulting are complicated by—
10. The multiplication of effects: every mass and part of a mass on which a force falls sub-divides and differentiates that force, which thereupon proceeds to work a variety of changes; and each of these becomes the parent of similarly multiplying changes: the multiplication of these becoming greater in proportion as the aggregate becomes more heterogeneous. And these two causes of increasing differentiations are furthered by—
11. Segregation, which is a process tending ever to separate unlike units, and to bring together like units, so serving continually to sharpen or make definite differentiations otherwise caused.
12. Equilibration is the final result of these transformations which an evolving aggregate undergoes. The changes go on until there is reached an equilibrium between the forces which all parts of the aggregate are exposed to, and the forces these parts oppose to them. Equilibration may pass through a transition stage of balanced motions (as in a planetary system), or of balanced functions (as in a living body), on the way to ultimate equilibrium; but the state of rest in inorganic bodies, or death in organic bodies, is the necessary limit of the changes constituting evolution.
13. Dissolution is the counterchange which sooner or later every evolved aggregate undergoes. Remaining exposed to surrounding forces that are unequilibrated, each aggregate is ever liable to be dissipated by the increase, gradual or sudden, of its contained motion; and its dissipation, quickly undergone by bodies lately animate, and slowly undergone by inanimate masses, remains to be undergone at an indefinitely remote period by each planetary and stellar mass, which, since an indefinitely remote period in the past, has been slowly evolving: the cycle of its transformations being thus completed.
14. This rhythm of evolution and dissolution, completing itself during short periods in small aggregates, and in the vast aggregates distributed through space completing itself in periods which are immeasurable by human thought, is, so far as we can see, universal and eternal: each alternating phase of the process predominating—now in this region of space, and now in that—as local conditions determine.
15. All these phenomena, from their great features down to their minutest details, are necessary results of the persistence of force under its forms of matter and motion. Given these in their known distributions through space, and their quantities being unchangeable, either by increase or decrease, there inevitably result the continuous redistributions distinguishable as evolution and dissolution, as well as all those special traits above enumerated.
16. That which persists, unchanging in quantity, but ever-changing in form, under these sensible appearances which the universe presents to us, transcends human knowledge and conception; is an unknown and an unknowable power, which we are obliged to recognise as without limit in space, and without beginning or end in time.
And the universal formula of Evolution stands thus: "Evolution is an integration of matter and concomitant dissipation of motion; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity; and during which the retained motion undergoes a parallel transformation" (First Principles, p. 396).
Notes and Queries.—(1) It should be noted that Spencer never suggested that he had explained the origin of things. On the contrary, "While the genesis of the Solar System, and of countless other systems like it, is thus rendered comprehensible, the ultimate mystery remains as great as ever. The problem of existence is not solved: it is simply moved further back." What he offered was a genetic description, and that is all that the scientific evolutionist ever offers.
(2) In the strict sense Spencer was no materialist. "Though the relation of subject and object renders necessary to us these antithetical conceptions of Spirit and Matter, the one is no less than the other to be regarded as but a sign of the Unknown Reality which underlies both." "Matter, Motion, and Force are but symbols of the Unknown Reality." "Only in a doctrine which recognises the Unknown Cause as co-extensive with all orders of phenomena, can there be a consistent Religion, or a consistent Philosophy." "Were we compelled to choose between the alternatives of translating mental phenomena into physical phenomena, or of translating physical phenomena into mental phenomena, the latter alternative would seem the more acceptable of the two."
It is one of the difficulties of Spencer's system that even when he is using physical concepts he is thinking of these not merely as symbols by which to formulate the routine of our sense-experience, but as symbols of the reality behind matter and motion of which we do not know anything. He works with the concept which he calls "the persistence of force," and when the reader is feeling its inadequacy to meet the situation, he is bluffed by the reminder—"By persistence of force we really mean the persistence of some Power which transcends our knowledge and conception": "Asserting the persistence of Force is but another mode of asserting an Unconditioned Reality without beginning or end."
(3) When an investigator in giving an account of a process insists on using higher categories than the sequences appear to require, he is guilty of "a transcendentalism," e.g., if he says that an instinctive action is rational, or that digestion is a psychical process. Similarly, when an investigator in giving an account of a process insists on using lower categories than the sequences appear to require, he is guilty of "a materialism," e.g., if he says that a rational act is simply a higher reflex, or that digestion is simply a chemical reaction. Therefore, although Spencer was not a materialist, we think that he was guilty of gross "materialisms," of attempting to give a false simplicity to the facts, e.g., in his attempt to trace the evolution of mind in terms of the evolution of the nervous system, and in his universal evolution-formula which is wholly in terms of Matter and Motion.
(4) By keeping throughout to mechanical categories, Spencer gives a semblance of simplicity and precision to his evolutionism, and his skill is such that the unwary reader is led gently on from orders of facts where mechanical categories (if not Spencer's) do certainly suffice, to other orders of facts—in immaterial evolution—where they seem strangely irrelevant. But if the reader, having his suspicions aroused by sundry jolts and jars in the onward sweep of the chariot of First Principles, begins to inquire into the reality of the apparent mechanical precision, he is likely to be disillusioned. Thus, at an early stage, he may discover that Spencer uses the word "force" without special definition in at least five senses,[11] which is not reassuring.
[11] See Karl Pearson. The Grammar of Science, p. 329.
As we have no expertness in these matters, we would submit the verdict of a recognised authority, Prof. Karl Pearson. One of Spencer's principles is "the redistribution of force," which he states in the following words:—
"A decreasing quantity of motion, sensible or insensible, always has for its concomitant an increasing aggregation of matter, and conversely an increasing quantity of motion, sensible or insensible, has for its concomitant a decreasing aggregation of matter."
In regard to this Prof. Pearson remarks: "This principle has, so far as I am aware, no real foundation in physics... it seems, so far as I can grasp it at all, to flatly contradict the modern principle of the conservation of energy"... the keystone of Spencer's system.
(5) What has taken place since Spencer stereotyped his First Principles seems to us to have rendered it almost useless to attempt a detailed criticism of his scheme of evolution—wonderful and stimulating as it was and is. He spoke of his delight in "intellectual hunting," and a great huntsman he certainly was, but the venue has changed since his day. He did not fully nor always rightly utilise the chemistry and physics of his time, and we have now to deal with a new chemistry and a new physics.
Mr J. B. Crozier speaks of Spencer as "of all thinkers ancient or modern the one whose power of analysing, decomposing, and combining the complex web of Matter, Motion, and Force is the most incontestable and assured." He describes Spencer's system as "No mere logical castle built of air and definitions, and assuming in its premises, like the systems of the metaphysicians, the very difficulties to be explained, but a great granite pile sunk deep in the bed-rock of the world, each stone a scientific truth, and all so compacted and dove-tailed together that it was difficult to find anywhere a logical flaw among their seams."
This is one view, but another will be found in Prof. James Ward's Gifford Lectures on "Naturalism and Agnosticism," in Mr Malcolm Guthrie's three volumes of criticism, and in several luminous papers by Principal James Iverach.
When we think of the evolution of the world and all that is therein—of a universal process of Becoming—we recognise that at an uncertain time the earth was framed, that living organisms appeared by and by, that by and by some of these exhibited mental as well as bodily life, and that finally man emerged, a rational and social person. This is a convenient and unified retrospect, but when we go further and say that all this evolution is expressible in one descriptive formula whose terms are mechanical, we are going further than our present knowledge warrants. Even Spencer did not really carry his evolution-formula throughout, for he admitted that "the development of Mind itself cannot be explained by a series of deductions from the Persistence of Force," though he covered his retreat by the suggestion that Mind is the subjective concomitant of the objective nervous system which has been evolved according to formula. But even if this tour de force seemed legitimate, we should still be unable to accept a universal formula of Evolution in terms of mechanism. For we are not at present able to think of the facts of bodily life in terms of mechanical categories. Thus, in short, when we enter the chariot of Spencer's Evolution-formula, and attempt to make an intellectual journey—"one and continuous" from the primitive nebula to human society, we confess to suffering serious joltings. We must admit that on that chariot at least we have never been able to arrive. Let us refer briefly to three of the worst jolts—at the origin of Life, at the origin of Mind, at the origin of Man.
Origin of Life.—It is much to be regretted that Spencer "had to omit that part of the System of Philosophy, which deals with Inorganic Evolution. Two volumes are missing." The closing chapter of the second volume was to have dealt with "the evolution of organic matter—the step preceding the evolution of living forms." It is tantalising to learn that he habitually carried with him in thought the contents of this unwritten chapter, for it would certainly have been interesting reading. He did, however, give us some hint of his views.
First of all negatively, Spencer did not believe in any alleged cases of spontaneous generation; he did not believe that any creature like an Infusorian could arise from not-living matter; he did not believe in an "absolute commencement of organic life," or in a "first organism." But just as the chemist is able to build up complex organic compounds from simple substances, so Spencer supposed that organic compounds were evolved in nature. He supposed the evolution of some substance like protein, which is capable of existing in many isomeric forms, and of forming with itself and other elements, substances yet more intricate in composition. "To the mutual influences of its metamorphic forms under favouring conditions, we may ascribe the production of the still more composite, still more sensitive, still more variously-changeable portions of organic matter, which, in masses more minute and simpler than existing Protozoa, displayed actions verging little by little into those called vital." By a continuance of the process, the nascent life displayed became gradually more pronounced.
No one who is aware of recent achievements in chemical synthesis, or of the recent "vitalising" of the concept of matter, or of the apparent simplicity of life in its humblest expressions, will seek to foreclose the question of the possible origin of living matter from not-living matter. The conclusion which most biologists accept is, that while there is no known evidence of not-living matter giving origin to living organisms, this does not exclude (a) the possibility that this once took place, or (b) the possibility that it may be made to take place again. It must always be remembered, however, that there is a great gap between a drop of living matter and an integrated living organism. We may firmly say that if living matter was once evolved from not-living matter, it must have been the outcome of long preparatory processes, that if it occurred, we cannot at present suggest "how" except in the vaguest way, and that if we knew it had occurred we should still be unable to explain the organism in terms of its antecedents.
Evolution of Mind.—Spencer speaks of the evolution-process as one and continuous throughout, but he felt, as other thorough-going evolutionists feel, that the emergence of psychical phenomena is a difficulty in the way of unified formulation.
"Let it be granted that all existence distinguished as objective, may be resolved into the existence of units of one kind. Let it be granted that every species of objective activity may be understood as due to the rhythmical motions of such ultimate units; and that among the objective activities so understood, are the waves of molecular motion propagated through nerves and nerve-centres. And let it further be granted that all existence distinguished as subjective, is resolvable into units of consciousness similar in nature to those which we know as nervous shocks; each of which is the correlative of a rhythmical motion of a material unit, or group of units. Can we then think of the subjective and objective activities as the same? Can the oscillation of a molecule be represented in consciousness side by side with a nervous shock, and the two be recognised as one? No effort enables us to assimilate them. That a unit of feeling has nothing in common with a unit of motion, becomes more than ever manifest when we bring the two into juxtaposition" (Principles of Psychology, i. p. 158).
He concluded that "there is not the remotest possibility of interpreting Mind in terms of Matter." Since our "ideas of Matter and Motion, merely symbolic of unknowable realities, are complex states of consciousness built out of units of feeling," "it seems easier to translate so-called Matter into so-called Spirit, than to translate so-called Spirit into so-called Matter, which latter is, indeed, wholly impossible."
The obvious difficulty, of which Spencer was well aware, is "how mental evolution is to be affiliated on Evolution at large, regarded as a process of physical transformation?
"Specifically stated, the problem is to interpret mental evolution in terms of the redistribution of Matter and Motion. Though under its subjective aspect Mind is known only as an aggregate of states of consciousness, which cannot be conceived as forms of Matter and Motion, and do not therefore necessarily conform to the same laws of redistribution; yet under its objective aspect, Mind is known as an aggregate of activities manifested by an organism—is the correlative, therefore, of certain material transformations, which must come within the general process of material evolution, if that process is truly universal. Though the development of Mind itself cannot be explained by a series of deductions from the Persistence of Force, yet it remains possible that its obverse, the development of physical changes in a physical organ, may be so explained; and until it is so explained, the conception of mental evolution as a part of Evolution in general, remains incomplete" (Principles of Psychology, i. p. 508).
Therefore Spencer passes to discuss the genesis of nervous systems and nervous functions, and by treating Mind as a mere aspect or epiphenomenon, eventually gets "an adequate explanation of nervous evolution, and the concomitant evolution of Mind," the Ultimate Reality being always postulated as the amalgam.
"See then our predicament. We can think of Matter only in terms of Mind. We can think of Mind only in terms of Matter, when we have pushed our explorations of the first to the uttermost limit, we are referred to the second for a final answer; and when we have got the final answer of the second, we are referred back to the first for an interpretation of it. We find the value of x in terms of y; then we find the value of y in terms of x; and so on we may continue for ever without coming nearer to a solution. The antithesis of subject and object, never to be transcended while consciousness lasts, renders impossible all knowledge of that Ultimate Reality in which subject and object are united" (Principles of Psychology, i. 627).
Ascent of Man.—Spencer was careful to say that it is not necessary to suppose "an absolute commencement of social life" or "a first social organism." But an ascent has to be accounted for however gradual the inclined plane may be, and like the origin of life, and the evolution of mind, the ascent of man to the level of a rational and social person is a very difficult problem, to the solution of which Spencer paid relatively little attention.
From our frankly biological point of view there seems considerable warrant for the suggestion that Man arose as a saltatory or transilient variation or "sport" in a gregarious Simian stock, which was not too hard-pressed by a struggle for subsistence either as regards food or climate, which was not too severely menaced by ever-persecuting stronger foes, which lived in conditions implying some measure of temporary isolation, in-breeding, and daily "brain-stretching" education. It seems likely that the transilient advance was in the direction of increased cerebral complexity, associated with greater freedom of speech, and a strengthened sense of kinship. It may be imagined that the advance occurred in times of relative peace and in a stimulating environment, where the seasons were well-defined, or where recurrent vicissitudes gave an advantage to memory and capacity for prevision.
Various useful suggestions have been made as to the possible factors in the evolution of man. (a) When the incipient man with his growing brain got on to his hind-legs, and walked more or less erect upon the earth, the new attitude, however prompted, would leave the hands more free for manipulation, for using a stone, a tool, or a weapon, for feeling round things and appreciating their three dimensions, it would react on other parts of the body, such as the spinal column, the pelvis, and perhaps even the larynx. In his address to the Anthropological Section of the British Association in 1893, Dr Robert Munro directed attention to three propositions: (1) the mechanical and physical advantages of the erect position, (2) the consequent differentiation of the limbs into hands and feet, and (3) the causal relation between this and the development of the brain.
(b) Fiske and others have called attention to the prolonged helpless infancy, so characteristic of human offspring, and illustrated in a less marked degree among Simian races. It would tend, in conditions not too severe, to tighten the family bond, and to evolve gentleness and a habit of altruistic outlook. It should also be remembered that the type of brain which characterises man is marked by its relative poverty in inherited instinct and by its eminent educability.
(c) The influence of the family was probably an important factor, fostering sympathy and mutual aid, prompting talk and division of labour. Even in early days, children would educate their parents. It must be remembered that many animals exhibit family life, and also pairing for prolonged periods or for life.
(d) If we grant the incipient man a growing, plastic, and restless brain, a strong feeling of kinship, some family ties, an erect attitude, the habit of using his hands and voice, all of which the anthropoid analogy suggests, and if we deny him sufficient physical strength to keep his foothold by virtue of that alone, then it seems more than a platitude to say that natural selection would favour the development of wits, and not only of wits, but in the widest sense (partly through sexual selection) of "love," which became a new source of strength.
(e) With the development of tool-using and sentence-making, with recognition of the seasons as a fundamental illustration of the uniformity of nature, with the gaining of a firmer foothold in the struggle for existence, with slowly increasing altruism and sociality, and with the occasional emergence of the genius, there might gradually arise—in permanent products, in symbols and songs, in traditions and customs—an external heritage, which, it appears to us, has been the most potent factor in securing and furthering human evolution.
Ignorant as we are as to the factors in human evolution, there is a convergence of various lines of evidence towards the conclusion that man must have come of a social stock. It is difficult to conceive of his survival on any other supposition. In a deeper sense, perhaps, than Rousseau thought of, it seems true that Man did not make Society, Society (pre-human) made Man.
By some means or other, probably along various paths—through kinship-sympathies, through linguistic bonds, for economic or life-and-death reasons, man became definitely social, and a new order of things began, which Spencer has pictured with great skill. Just as it was a new event in the history of Hymenopterous insects when ants made an ant-hill, or bees a natural hive, so it was a new event in the history of Man when unified societary groups came into being.
Now all this is vague, and, it may be, unconvincing; but we are not aware that Spencer had any further light to throw on the problem—a problem so difficult that Alfred Russel Wallace, the Nestor among living evolutionists, has declared his conviction that the development of man's higher qualities cannot be conceived without postulating "spiritual influx." Our point at present is that the difficulties are greater than Spencer publicly recognised, and that his formula of evolution is not only too remotely abstract to be relevant, but that it is in its mechanical phrasing quite inapplicable.
The Scientific Position.—The idea of organic evolution suggests—that the forms of life have had a natural history, that they have descended from a far-distant relatively simple ancestry, that they have risen from level to level throughout many millions of years just as individual animals in their development rise from level to level in a few days or months or years. It is the only scientific conception we have of the Becoming of the world of life.
The theory of organic evolution raises this modal interpretation into a causal interpretation by disclosing the factors—such as Variation and Selection—in the long process. To some minds, the known factors appear inadequate to describe the process, especially in relation to the emergence of mental life and the ascent of man. Thus an attempt is often made to sit on both sides of the fence, accepting scientific factors for what they are worth, but eking them out by postulating "ultra-scientific" causes. This procedure, however, lands in mental confusion; it is like trying to speak two languages at once. It is also very premature.
When we extend the concept of evolution to the inorganic world, we find that it applies there also, that it enables us to resume the history of the solar system as a whole, and of the earth in particular in a convenient formula. Here again we are aware of factors of evolution, which enable us to give a causal interpretation of how the inanimate world came to be as it is. The factors are not the same as those verifiable in organic evolution; they are in terms of the laws of motion and other physical concepts.
Again the idea of evolution may be applied to the forms of mental life and to the forms of social life, and in these realms the factors are not the same as those used in interpreting the history of organisms (objectively considered) or the history of inanimate systems.
In all cases the general concept of evolution is the same—the idea of natural progressive change—but the factors are different. The reason for this is that the organism is very different from a planet or a crystal, that mind is quite different from metabolism, that a society is more than the sum of its parts.
It is quite plain that the sociological evolutionist will not advance far if he disregards the concept of the social organism, if he shuts his eyes to the fact that a societary form, however simple, is an integrate; not a mere congeries of persons, but a unity with a life and mind of its own. Yet he may quite consistently try to trace the emergence of societary forms from a simply gregarious stock, and that again from entirely non-social organisms.
In the same way the psychological evolutionist will not advance far if he disregards the distinctiveness of mental life, with principles of its own quite different from those of the bodily life with which it is inextricably associated. That is to say he must be more than a physiologist of the nervous system.
So, the biological evolutionist must admit that he cannot trace the evolution of organisms in terms of the concepts which suffice for inanimate systems. In so doing he does not dogmatically say that the activity of organisms cannot be described in terms of mechanism, he only says that it has not been done; he only says that neither physics nor physiology is at present within sight of deducing the laws of motion of organic corpuscles from the laws of motion of other corpuscles.
There is no reason why he should stand aloof from the theory that inorganic and organic evolution are continuous, in other words from the theory of the spontaneous generation of living matter at an appropriate time in the Earth's history—a theory which is suggested by many facts. If that is a legitimate theory it increases our respect for what we call the inanimate, but it does not make our biological evolutionism any easier, nor are we any nearer explaining life. The organism remains what it is, a living creature with a behaviour which we are unable to redescribe in terms of mechanism. And inanimate matter remains what it is, except that we should be able to say definitely that it had once given origin to living matter and might conceivably do so again. There would be no gain in adding to the properties of matter a mysterious "capacity-of-sharing-in-the-spontaneous-generation-of-life."
Let us state the position once more. When one of the higher animals, in the course of its development, reaches a certain, or rather uncertain, degree of differentiation, its functioning becomes behaviour; its activities are such that we cannot interpret them without using psychical terms, such as awareness or intelligence. This expression of fuller life is associated with the increased development of the nervous system, and we have no knowledge of any psychical life apart from nervous metabolism. Yet we remain quite unable to think of any way by which the metabolism of nerve-cells gives rise to what we know in ourselves as sensations or perceptions, ideas or feelings. Therefore while we see no reason to doubt the continuity of the individual development, we recognise as fact of experience that the merely sentient embryo becomes a thoughtful child, whose behaviour cannot be formulated in terms of our present biological or our present mechanical categories.
And as it is with the individual development, so it is with the evolution of organisms; when they exhibit a certain, or rather uncertain, degree of differentiation they behave in a way which we cannot interpret without using psychical terms. We know of very simple forms whose whole behaviour seems to be summed up in one reflex action, at least if there is more we cannot detect it; we know of other unicellular animals whose behaviour is such that we are forced to say that they seem to pursue the method of trial and error; and from that level we know of a long inclined plane leading up to very alert intelligence. Again we see no reason to doubt the continuity of the process, though we recognise that at a certain level of organisation the biological categories of metabolism and the like are no longer sufficient to formulate the facts. How it is that the activity of the nervous system does express itself in such a way, that we must use a new set of terms—psychical ones—to cover the facts of behaviour, no one has at present any conception. A living creature behaves in such a way that we cannot interpret what it does in terms of the motions of the organic corpuscles which compose it. We do not know how to formulate in physical terms its growth, its development, its power of effective response, its co-ordination of activities. Therefore we introduce a special series of biological concepts, without denying that a greater unity of formulation may some day be attained either by a further simplification of the biological concepts or by some change in the physical concepts, such as, indeed, seems coming about at present.
But again, a living creature behaves in such a way that our biological concepts are insufficient to formulate its behaviour. We do not know how to interpret what it does without psychological concepts of thinking, feeling, and willing. It is possible that here, too, a greater unity of formulation may some day be attained either by a further simplification of the psychological concepts or by some change in the biological concepts. But sufficient unto the day is the science thereof.