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## CHAPTER XX.: THE MULTIPLICATION OF EFFECTS. - Herbert Spencer, First Principles [1867]

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First Principles, 2nd ed. (London: Williams and Norgate, 1867).

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### THE MULTIPLICATION OF EFFECTS.

§ 156. To the cause of increasing complexity set forth in the last chapter, we have in this chapter to add another. Though secondary in order of time, it is scarcely secondary in order of importance. Even in the absence of the cause already assigned, it would necessitate a change from the homogeneous to the heterogeneous; and joined with it, it makes this change both more rapid and more involved. To come in sight of it, we have but to pursue a step further, that conflict between force and matter already delineated. Let us do this.

When a uniform aggregate is subject to a uniform force, we have seen that its constituents, being differently conditioned, are differently modified. But while we have contemplated the various parts of the aggregate as thus undergoing unlike changes, we have not yet contemplated the unlike changes simultaneously produced on the various parts of the incident force. These must be as numerous and important as the others. Action and re-action being equal and opposite, it follows that in differentiating the parts on which it falls in unlike ways, the incident force must itself be correspondingly differentiated. Instead of being as before, a uniform force, it must thereafter be a multiform force—a group of dissimilar forces. A few illustrations will make this truth manifest.

A single force is divided by conflict with matter into forces that widely diverge. In the case lately cited, of a body shattered by violent collision, besides the change of the homogeneous mass into a heterogeneous group of scattered fragments, there is a change of the homogeneous momentum into a group of momenta, heterogeneous in both amounts and directions. Similarly with the forces we know as light and heat. After the dispersion of these by a radiating body towards all points, they are re-dispersed towards all points by the bodies on which they fall. Of the Sun’s rays, issuing from him on every side, some few strike the Moon. These being reflected at all angles from the Moon’s surface, some few of them strike the Earth. By a like process the few which reach the Earth are again diffused through surrounding space. And on each occasion, such portions of the rays as are absorbed instead of reflected, undergo refractions that equally destroy their parallelism. More than this is true. By conflict with matter, a uniform force is in part changed into forces differing in their directions; and in part it is changed into forces differing in their kinds. When one body is struck against another, that which we usually regard as the effect, is a change of position or motion in one or both bodies. But a moment’s thought shows that this is a very incomplete view of the matter. Besides the visible mechanical result, sound is produced; or, to speak accurately, a vibration in one or both bodies, and in the surrounding air: and under some circumstances we call this the effect. Moreover, the air has not simply been made to vibrate, but has had currents raised in it by the transit of the bodies. Further, if there is not that great structural change which we call fracture, there is a disarrangement of the particles of the two bodies around their point of collision; amounting in some cases to a visible condensation. Yet more, this condensation is accompanied by disengagement of heat. In some cases a spark—that is, light—results, from the incandescence of a portion struck off; and occasionally this incandescence is associated with chemical combination. Thus, by the original mechanical force expended in the collision, at least five, and often more, different kinds of forces have been produced. Take, again, the lighting of a candle. Primarily, this is a chemical change consequent on a rise of temperature. The process of combination having once been set going by extraneous heat, there is a continued formation of carbonic acid, water, &c.—in itself a result more complex than the extraneous heat that first caused it. But along with this process of combination there is a production of heat; there is a production of light; there is an ascending column of hot gases generated; there are currents established in the surrounding air. Nor does the decomposition of one force into many forces end here. Each of the several changes worked becomes the parent of further changes. The carbonic acid formed, will by and by combine with some base; or under the influence of sunshine give up its carbon to the leaf of a plant. The water will modify the hygrometric state of the air around; or, if the current of hot gases containing it come against a cold body, will be condensed: altering the temperature, and perhaps the chemical state, of the surface it covers. The heat given out melts the subjacent tallow, and expands whatever it warms. The light, falling on various substances, calls forth from them reactions by which it is modified; and so divers colours are produced. Similarly even with these secondary actions, which may be traced out into ever-multiplying ramifications, until they become too minute to be appreciated. Universally, then, the effect is more complex than the cause. Whether the aggregate on which it falls be homogeneous or otherwise, an incident force is transformed by the conflict into a number of forces that differ in their amounts, or directions, or kinds; or in all these respects. And of this group of variously-modified forces, each ultimately undergoes a like transformation.

Let us now mark how the process of evolution is furthered by this multiplication of effects. An incident force decomposed by the reactions of a body into a group of unlike forces—a uniform force thus reduced to a multiform force—becomes the cause of a secondary increase of multiformity in the body which decomposes it. In the last chapter we saw that the several parts of an aggregate are differently modified by any incident force. It has just been shown that by the reactions of the differently modified parts, the incident force itself must be divided into differently modified parts. Here it remains to point out that each differentiated division of the aggregate, thus becomes a centre from which a differentiated division of the original force is again diffused. And since unlike forces must produce unlike results, each of these differentiated forces must produce, throughout the aggregate, a further series of differentiations. This secondary cause of the change from homogeneity to heterogeneity, obviously becomes more potent in proportion as the heterogeneity increases. When the parts into which any evolving whole has segregated itself, have diverged widely in nature, they will necessarily react very diversely on any incident force—they will divide an incident force into so many strongly contrasted groups of forces. And each of them becoming the centre of a quite distinct set of influences, must add to the number of distinct secondary changes wrought throughout the aggregate. Yet another corollary must be added. The number of unlike parts of which an aggregate consists, as well as the degree of their unlikeness, is an important factor in the process. Every additional specialized division is an additional centre of specialized forces. If a uniform whole, in being itself made multiform by an incident force, makes the incident force multiform; if a whole consisting of two unlike sections, divides an incident force into two unlike groups of multiform forces; it is clear that each new unlike section must be a further source of complication among the forces at work throughout the mass—a further source of heterogeneity. The multiplication of effects must proceed in geometrical progression. Each stage of evolution must initiate a higher stage.

§ 157. The force of aggregation acting on irregular masses of rare matter, diffused through a resisting medium, will not cause such masses to move in straight lines to their common centre of gravity; but, as before said, each will take a curvilinear path, directed to one or other side of the centre of gravity. All of them being differently conditioned, gravitation will impress on each a motion differing in direction, in velocity, and in the degree of its curvature—uniform aggregative force will be differentiated into multiform momenta. The process thus commenced, must go on till it produces a single mass of nebulous matter; and these independent curvilinear motions must result in a movement of this mass round its axis: a simultaneous condensation and rotation in which we see how two effects of the aggregative force, at first but slightly divergent, become at last widely differentiated. A gradual increase of oblateness in this revolving spheroid, must take place through the joint action of these two forces, as the bulk diminishes and the rotation grows more rapid; and this we may set down as a third effect. The genesis of heat, which must accompany augmentation of density, is a consequence of yet another order—a consequence by no means simple; since the various parts of the mass, being variously condensed, must be variously heated. Acting throughout a gaseous spheroid, of which the parts are unlike in their temperatures, the forces of aggregation and rotation must work a further series of changes: they must set up circulating currents, both general and local. At a later stage light as well as heat will be generated. Thus without dwelling on the likelihood of chemical combinations and electric disturbances, it is sufficiently manifest that, supposing matter to have originally existed in a diffused state, the once uniform force which caused its aggregation, must have become gradually divided into different forces; and that each further stage of complication in the resulting aggregate, must have initiated further subdivisions of this force—a further multiplication of effects, increasing the previous heterogeneity.

This section of the argument may however be adequately sustained, without having recourse to any such hypothetical illustrations as the foregoing. The astronomical attributes of the Earth, will even alone suffice our purpose. Consider first the effects of its momentum round its axis. There is the oblateness of its form; there is the alternation of day and night; there are certain constant marine currents; and there are certain constant aërial currents. Consider next the secondary series of consequences due to the divergence of the Earth’s plane of rotation from the plane of its orbit. The many differences of the seasons, both simultaneous and successive, which pervade its surface, are thus caused. External attraction acting on this rotating oblate spheroid with inclined axis, produces the motion called nutation, and that slower and larger one from which follows the precession of the equinoxes, with its several sequences. And then by this same force are generated the tides, aqueous and atmospheric.

Perhaps, however, the simplest way of showing the multiplication of effects among phenomena of this order, will be to set down the influences of any member of the Solar System on the rest. A planet directly produces in neighbouring planets certain appreciable perturbations, complicating those otherwise produced in them; and in the remoter planets it directly produces certain less visible perturbations. Here is a first series of effects. But each of the perturbed planets is itself a source of perturbations—each directly affects all the others. Hence, planet A having drawn planet B out of the position it would have occupied in A’s absence, the perturbations which B causes are different from what they would else have been; and similarly with C, D, E, &c. Here then is a secondary series of effects: far more numerous though far smaller in their amounts. As these indirect perturbations must to some extent modify the movements of each planet, there results from them a tertiary series; and so on continually. Thus the force exercised by any planet works a different effect on each of the rest; this different effect is from each as a centre partially broken up into minor different effects on the rest; and so on in ever multiplying and diminishing waves throughout the entire system.

§ 158. If the Earth was formed by the concentration of diffused matter, it must at first have been incandescent; and whether the nebular hypothesis be accepted or not, this original incandescence of the Earth must now be regarded as inductively established—or, if not established, at least rendered so probable that it is a generally admitted geological doctrine. Several results of the gradual cooling of the Earth—as the formation of a crust, the solidification of sublimed elements, the precipitation of water, &c., have been already noticed—and I here again refer to them merely to point out that they are simultaneous effects of the one cause, diminishing heat. Let us now, however, observe the multiplied changes afterwards arising from the continuance of this one cause. The Earth, falling in temperature, must contract. Hence the solid crust at any time existing, is presently too large for the shrinking nucleus; and being unable to support itself, inevitably follows the nucleus. But a spheroidal envelope cannot sink down into contact with a smaller internal spheroid, without disruption: it will run into wrinkles, as the rind of an apple does when the bulk of its interior decreases from evaporation. As the cooling progresses and the envelope thickens, the ridges consequent on these contractions must become greater; rising ultimately into hills and mountains; and the later systems of mountains thus produced must not only be higher, as we find them to be, but they must be longer, as we also find them to be. Thus, leaving out of view other modifying forces, we see what immense heterogeneity of surface arises from the one cause, loss of heat—a heterogeneity which the telescope shows us to be paralleled on the Moon, where aqueous and atmospheric agencies have been absent. But we have yet to notice another kind of heterogeneity of surface, similarly and simultaneously caused. While the Earth’s crust was still thin, the ridges produced by its contraction must not only have been small, but the tracts between them must have rested with comparative smoothness on the subjacent liquid spheroid; and the water in those arctic and antarctic regions where it first condensed, must have been evenly distributed. But as fast as the crust grew thicker and gained corresponding strength, the lines of fracture from time to time caused in it, necessarily occurred at greater distances apart; the intermediate surfaces followed the contracting nucleus with less uniformity; and there consequently resulted larger areas of land and water. If any one, after wrapping an orange in wet tissue paper, and observing both how small are the wrinkles and how evenly the intervening spaces lie on the surface of the orange, will then wrap it in thick cartridge-paper, and note both the greater height of the ridges and the larger spaces throughout which the paper does not touch the orange, he will realize the fact, that as the Earth’s solid envelope thickened, the areas of elevation and depression became greater. In place of islands more or less homogeneously scattered over an all-embracing sea, there must have gradually arisen heterogeneous arrangements of continent and ocean, such as we now know. This double change in the extent and in the elevation of the lands, involved yet another species of heterogeneity—that of coast-line. A tolerably even surface raised out of the ocean will have a simple, regular sea-margin; but a surface varied by tablelands and intersected by mountain-chains, will, when raised out of the ocean, have an outline extremely irregular, alike in its leading features and in its details. Thus endless is the accumulation of geological and geographical results slowly brought about by this one cause—the escape of the Earth’s primitive heat.

When we pass from the agency which geologists term igneous, to aqueous and atmospheric agencies, we see a like ever-growing complication of effects. The denuding actions of air and water have, from the beginning, been modifying every exposed surface: everywhere working many different changes. As already shown (§ 69) the original source of those gaseous and fluid motions which effect denudation, is the solar heat. The transformation of this into various modes of force, according to the nature and condition of the matter on which it falls, is the first stage of complication. The sun’s rays, striking at all angles a sphere, that from moment to moment presents and withdraws different parts of its surface, and each of them for a different time daily throughout the year, would produce a considerable variety of changes even were the sphere uniform. But falling as they do on a sphere surrounded by an atmosphere in some parts of which wide areas of cloud are suspended, and which here unveils vast tracts of sea, there of level land, there of mountains, there of snow and ice, they initiate in its several parts countless different movements. Currents of air of all sizes, directions, velocities, and temperatures, are set up; as are also marine currents similarly contrasted in their characters. In this region the surface is giving off water in the state of vapour; in that, dew is being precipitated; and in the other rain is descending—differences that arise from the ever-changing ratio between the absorption and radiation of heat in each place. At one hour, a rapid fall in temperature leads to the formation of ice, with an accompanying expansion throughout the moist bodies frozen; while at another, a thaw unlocks the dislocated fragments of these bodies. And then, passing to a second stage of complication, we see that the many kinds of motion directly or indirectly caused by the sun’s rays, severally produce results that vary with the conditions. Oxidation, drought, wind, frost, rain, glaciers, rivers, waves, and other denuding agents effect disintegrations that are determined in their amounts and qualities by local circumstances. Acting upon a tract of granite, such agents here work scarcely an appreciable effect; there cause exfoliations of the surface, and a resulting heap of débris and boulders; and elsewhere, after decomposing the feldspar into a white clay, carry away this with the accompanying quartz and mica, and deposit them in separate beds, fluviatile and marine. When the exposed land consists of several unlike formations, sedimentary and igneous, changes proportionably more heterogeneous are wrought. The formations being disintegrable in different degrees, there follows an increased irregularity of surface. The areas drained by different rivers being differently constituted, these rivers carry down to the sea unlike combinations of ingredients; and so sundry new strata of distinct composition arise. And here indeed we may see very simply illustrated, the truth, that the heterogeneity of the effects increases in a geometrical progression, with the heterogeneity of the object acted upon. A continent of complex structure, presenting many strata irregularly distributed, raised to various levels, tilted up at all angles, must, under the same denuding agencies, give origin to immensely multiplied results: each district must be peculiarly modified; each river must carry down a distinct kind of detritus; each deposit must be differently distributed by the entangled currents, tidal and other, which wash the contorted shores; and every additional complication of surface must be the cause of more than one additional consequence. But not to dwell on these, let us, for the fuller elucidation of this truth in relation to the inorganic world, consider what would presently follow from some extensive cosmical revolution—say the subsidence of Central America. The immediate results of the disturbance would themselves be sufficiently complex. Besides the numberless dislocations of strata, the ejections of igneous matter, the propagation of earthquake vibrations thousands of miles around, the loud explosions, and the escape of gases, there would be the rush of the Atlantic and Pacific Oceans to supply the vacant space, the subsequent recoil of enormous waves, which would traverse both these oceans and produce myriads of changes along their shores, the corresponding atmospheric waves complicated by the currents surrounding each volcanic vent, and the electrical discharges with which such disturbances are accompanied. But these temporary effects would be insignificant compared with the permanent ones. The complex currents of the Atlantic and Pacific would be altered in directions and amounts. The distribution of heat achieved by these currents would be different from what it is. The arrangement of the isothermal lines, not only on the neighbouring continents, but even throughout Europe, would be changed. The tides would flow differently from what they do now. There would be more or less modification of the winds in their periods, strengths, directions, qualities. Rain would fall scarcely anywhere at the same times and in the same quantities as at present. In short, the meteorological conditions thousands of miles off, on all sides, would be more or less revolutionized. In these many changes, each of which comprehends countless minor ones, the reader will see the immense heterogeneity of the results wrought out by one force, when that force expends itself on a previously complicated area; and he will readily draw the corollary that from the beginning the complication has advanced at an increasing rate.

§ 159. We have next to trace throughout organic evolution, this same all-pervading principle. And here, where the transformation of the homogeneous into the heterogeneous was first observed, the production of many changes by one cause is least easy to demonstrate. The development of a seed into a plant, or an ovum into an animal, is so gradual; while the forces which determine it are so involved, and at the same time so unobtrusive; that it is difficult to detect the multiplication of effects which is elsewhere so obvious. Nevertheless, by indirect evidence we may establish our proposition; spite of the lack of direct evidence.

Observe, first, how numerous are the changes which any marked stimulus works on an adult organism—a human being, for instance. An alarming sound or sight, besides impressions on the organs of sense and the nerves, may produce a start, a scream, a distortion of the face, a trembling consequent on general muscular relaxation, a burst of perspiration, an excited action of the heart, a rush of blood to the brain, followed possibly by arrest of the heart’s action and by syncope; and if the system be feeble, an illness with its long train of complicated symptoms may set in. Similarly in cases of disease. A minute portion of the small-pox virus introduced into the system, will, in a severe case, cause, during the first stage, rigors, heat of skin, accelerated pulse, furred tongue, loss of appetite, thirst, epigastric uneasiness, vomiting, head-ache, pains in the back and limbs, muscular weakness, convulsions, delirium, &c.; in the second stage, cutaneous eruption, itching, tingling, sore throat, swelled fauces, salivation, cough, hoarseness, dyspnœa, &c.; and in the third stage, œdematous inflammations, pneumonia, pleurisy, diarrhœa, inflammation of the brain, ophthalmia, erysipelas, &c.; each of which enumerated symptoms is itself more or less complex. Medicines, special foods, better air, might in like manner be instanced as producing multiplied results. Now it needs only to consider that the many changes thus wrought by one force on an adult organism, must be partially paralleled in an embryo-organism, to understand how here also the production of many effects by one cause is a source of increasing heterogeneity. The external heat and other agencies which determine the first complications of the germ, will, by acting on these, superinduce further complications; on these still higher and more numerous ones; and so on continually: each organ as it is developed, serving, by its actions and reactions on the rest, to initiate new complexities. The first pulsations of the fœtal heart must simultaneously aid the unfolding of every part. The growth of each tissue, by taking from the blood special proportions of elements, must modify the constitution of the blood; and so must modify the nutrition of all the other tissues. The distributive actions, implying as they do a certain waste, necessitate an addition to the blood of effete matters, which must influence the rest of the system, and perhaps, as some think, initiate the formation of excretory organs. The nervous connections established among the viscera must further multiply their mutual influences. And so with every modification of structure—every additional part and every alteration in the ratios of parts. Still stronger becomes the proof when we call to mind the fact, that the same germ may be evolved into different forms according to circumstances. Thus, during its earlier stages, every embryo is sexless—becomes either male or female as the balance of forces acting on it determines. Again, it is well-known that the larva of a working-bee will develop into a queen-bee, if, before a certain period, its food be changed to that on which the larvæ of queen-bees are fed. Even more remarkable is the case of certain entozoa. The ovum of a tape-worm, getting into the intestine of one animal, unfolds into the form of its parent; but if carried into other parts of the system, or into the intestine of some unlike animal, it becomes one of the sac-like creatures, called by naturalists Cysticerci, or Cœnuri, or Echinococci—creatures so extremely different from the tape-worm in aspect and structure, that only after careful investigations have they been proved to have the same origin. All which instances imply that each advance in embryonic complication results from the action of incident forces on the complication previously existing. Indeed, the now accepted doctrine of epigenesis necessitates the conclusion that organic evolution proceeds after this manner. For since it is proved that no germ, animal or vegetal, contains the slightest rudiment, trace, or indication of the future organism—since the microscope has shown us that the first process set up in every fertilized germ is a process of repeated spontaneous fissions, ending in the production of a mass of cells, not one of which exhibits any special character; there seems no alternative but to conclude that the partial organization at any moment subsisting in a growing embryo, is transformed by the agencies acting on it into the succeeding phase of organization, and this into the next, until, through ever-increasing complexities, the ultimate form is reached. Thus, though the subtlety of the forces and the slowness of the metamorphosis, prevent us from directly tracing the genesis of many changes by one cause, throughout the successive stages which every embryo passes through; yet, indirectly, we have strong evidence that this is a source of increasing heterogeneity. We have marked how multi-tudinous are the effects which a single agency may generate in an adult organism; that a like multiplication of effects must happen in the unfolding organism, we have inferred from sundry illustrative cases; further, it has been pointed out that the ability which like germs have to originate unlike forms, implies that the successive transformations result from the new changes superinduced on previous changes; and we have seen that structureless as every germ originally is, the development of an organism out of it is otherwise incomprehensible. Doubtless we are still in the dark respecting those mysterious properties which make the germ, when subject to fit influences, undergo the special changes beginning this series of transformations. All here contended is, that given a germ possessing these mysterious properties, the evolution of an organism from it depends, in part, on that multiplication of effects which we have seen to be a cause of evolution in general, so far as we have yet traced it.

When, leaving the development of single plants and animals, we pass to that of the Earth’s flora and fauna, the course of the argument again becomes clear and simple. Though, as before admitted, the fragmentary facts Palæontology has accumulated, do not clearly warrant us in saying that, in the lapse of geologic time, there have been evolved more heterogeneous organisms, and more heterogeneous assemblages of organisms; yet we shall now see that there must ever have been a tendency towards these results. We shall find that the production of many effects by one cause, which, as already shown, has been all along increasing the physical heterogeneity of the Earth, has further necessitated an increasing heterogeneity in its flora and fauna, individually and collectively. An illustration will make this clear. Suppose that by a series of upheavals, occurring, as they are now known to do, at long intervals, the East Indian Archipelago were to be raised into a continent, and a chain of mountains formed along the axis of elevation. By the first of these upheavals, the plants and animals inhabiting Borneo, Sumatra, New Guinea, and the rest, would be subjected to slightly-modified sets of conditions. The climate in general would be altered in temperature, in humidity, and in its periodical variations; while the local differences would be multiplied. These modifications would affect, perhaps inappreciably, the entire flora and fauna of the region. The change of level would produce additional modifications; varying in different species, and also in different members of the same species, according to their distance from the axis of elevation. Plants, growing only on the sea-shore in special localities, might become extinct. Others, living only in swamps of a certain humidity, would, if they survived at all, probably undergo visible changes of appearance. While more marked alterations would occur in some of the plants that spread over the lands newly raised above the sea. The animals and insects living on these modified plants, would themselves be in some degree modified by change of food, as well as by change of climate; and the modification would be more marked where, from the dwindling or disappearance of one kind of plant, an allied kind was eaten. In the lapse of the many generations arising before the next upheaval, the sensible or insensible alterations thus produced in each species, would become organized—in all the races that survived there would be a more or less complete adaptation to the new conditions. The next upheaval would superinduce further organic changes, implying wider divergences from the primary forms; and so repeatedly. Now however let it be observed that this revolution would not be a substitution of a thousand modified species for the thousand original species; but in place of the thousand original species there would arise several thousand species, or varieties, or changed forms. Each species being distributed over an area of some extent, and tending continually to colonize the new area exposed, its different members would be subject to different sets of changes. Plants and animals migrating towards the equator would not be affected in the same way with others migrating from it. Those which spread towards the new shores, would undergo changes unlike the changes undergone by those which spread into the mountains. Thus, each original race of organisms would become the root from which diverged several races, differing more or less from it and from each other; and while some of these might subsequently disappear, probably more than one would survive in the next geologic period: the very dispersion itself increasing the chances of survival. Not only would there be certain modifications thus caused by changes of physical conditions and food; but also in some cases other modifications caused by changes of habit. The fauna of each island, peopling, step by step, the newly-raised tracts, would eventually come in contact with the faunas of other islands; and some members of these other faunas would be unlike any creatures before seen. Herbivores meeting with new beasts of prey, would, in some cases, be led into modes of defence or escape differing from those previously used; and simultaneously the beasts of prey would modify their modes of pursuit and attack. We know that when circumstances demand it, such changes of habit do take place in animals; and we know that if the new habits become the dominant ones, they must eventually in some degree alter the organization. Observe now, however, a further consequence. There must arise not simply a tendency towards the differentiation of each race of organisms into several races; but also a tendency to the occasional production of a somewhat higher organism. Taken in the mass, these divergent varieties, which have been caused by fresh physical conditions and habits of life, will exhibit alterations quite indefinite in kind and degree; and alterations that do not necessarily constitute an advance. Probably in most cases the modified type will be not appreciably more heterogeneous than the original one. But it must now and then occur, that some division of a species, falling into circumstances which give it rather more complex experiences, and demand actions somewhat more involved, will have certain of its organs further differentiated in proportionately small degrees—will become slightly more heterogeneous. Hence, there will from time to time arise an increased heterogeneity both of the Earth’s flora and fauna, and of individual races included in them. Omitting detailed explanations, and allowing for the qualifications which cannot here be specified, it is sufficiently clear that geological mutations have all along tended to complicate the forms of life, whether regarded separately or collectively. That multiplication of effects which has been a part-cause of the transformation of the Earth’s crust from the simple into the complex, has simultaneously led to a parallel transformation of the Life upon its surface.

The deduction here drawn from the established truths of geology and the general laws of life, gains immensely in weight on finding it to be in harmony with an induction drawn from direct experience. Just that divergence of many races from one race, which we inferred must have been continually occurring during geologic time, we know to have occurred during the pre-historic and historic periods, in man and domestic animals. And just that multiplication of effects which we concluded must have been instrumental to the first, we see has in a great measure wrought the last. Single causes, as famine, pressure of population, war, have periodically led to further dispersions of mankind and of dependent creatures: each such dispersion initiating new modifications, new varieties of type. Whether all the human races be or be not derived from one stock, philology makes it clear that whole groups of races, now easily distinguishable from each other, were originally one race—that the diffusion of one race into different climates and conditions of existence has produced many altered forms of it. Similarly with domestic animals. Though in some cases (as that of dogs) community of origin will perhaps be disputed, yet in other cases (as that of the sheep or the cattle of our own country) it will not be questioned that local differences of climate, food, and treatment, have transformed one original breed into numerous breeds, now become so far distinct as to produce unstable hybrids. Moreover, through the complication of effects flowing from single causes, we here find, what we before inferred, not only an increase of general heterogeneity, but also of special heterogeneity. While of the divergent divisions and subdivisions of the human race, many have undergone changes not constituting an advance; others have become decidedly more heterogeneous. The civilized European departs more widely from the vertebrate archetype than does the savage.

§ 160. A sensation does not expend itself in arousing some single state of consciousness; but the state of consciousness aroused is made up of various represented sensations connected by co-existence, or sequence with the presented sensation. And that, in proportion as the grade of intelligence is high, the number of ideas suggested is great, may be readily inferred. Let us, however, look at the proof that here too, each change is the parent of many changes; and that the multiplication increases in proportion as the area affected is complex.

Were some hitherto unknown bird, driven say by stress of weather from the remote north, to make its appearance on our shores, it would excite no speculation in the sheep or cattle amid which it alighted: a perception of it as a creature like those constantly flying about, would be the sole interruption of that dull current of consciousness which accompanies grazing and rumination. The cow-herd, by whom we may suppose the exhausted bird to be presently caught, would probably gaze at it with some slight curiosity, as being unlike any he had before seen—would note its most conspicuous markings, and vaguely ponder on the questions, where it came from, and how it came. The village bird-stuffer would have suggested to him by the sight of it, sundry forms to which it bore a little resemblance; would receive from it more numerous and more specific impressions respecting structure and plumage; would be reminded of various instances of birds brought by storms from foreign parts—would tell who found them, who stuffed them, who bought them. Supposing the unknown bird taken to a naturalist of the old school, interested only in externals, (one of those described by the late Edward Forbes, as examining animals as though they were merely skins filled with straw,) it would excite in him a more involved series of mental changes: there would be an elaborate examination of the feathers, a noting of all their technical distinctions, with a reduction of these perceptions to certain equivalent written symbols; reasons for referring the new form to a particular family, order, and genus would be sought out and written down; communications with the secretary of some society, or editor of some journal, would follow; and probably there would be not a few thoughts about the addition of the ii to the describer’s name, to form the name of the species. Lastly, in the mind of a comparative anatomist, such a new species, should it happen to have any marked internal peculiarity, might produce additional sets of changes—might very possibly suggest modified views respecting the relationships of the division to which it belonged; or, perhaps, alter his conceptions of the homologies and developments of certain organs; and the conclusions drawn might not improbably enter as elements into still wider inquiries concerning the origin of organic forms.

From ideas let us turn to emotions. In a young child, a father’s anger produces little else than vague fear—a disagreeable sense of impending evil, taking various shapes of physical suffering or deprivation of pleasures. In elder children, the same harsh words will arouse additional feelings: sometimes a sense of shame, of penitence, or of sorrow for having offended; at other times, a sense of injustice, and a consequent anger. In the wife, yet a further range of feelings may come into existence—perhaps wounded affection, perhaps self-pity for ill-usage, perhaps contempt for groundless irritability, perhaps sympathy for some suffering which the irritability indicates, perhaps anxiety about an unknown misfortune which she thinks has produced it. Nor are we without evidence that among adults, the like differences of development are accompanied by like differences in the number of emotions that are aroused, in combination or rapid succession—the lower natures being characterized by that impulsiveness which results from the uncontrolled action of a few feelings; and the higher natures being characterized by the simultaneous action of many secondary feelings, modifying those first awakened.

Possibly it will be objected that the illustrations here given, are drawn from the functional changes of the nervous system, not from its structural changes; and that what is proved among the first, does not necessarily hold among the last. This must be admitted. Those, however, who recognize the truth that the structural changes are the slowly accumulated results of the functional changes, will readily draw the corollary, that a part-cause of the evolution of the nervous system, as of other evolution, is this multiplication of effects which becomes ever greater as the development becomes higher.

§ 161. If the advance of Man towards greater heterogeneity in both body and mind, is in part traceable to the production of many effects by one cause, still more clearly may the advance of Society towards greater heterogeneity be so explained. Consider the growth of an industrial organization. When, as must occasionally happen, some individual of a tribe displays unusual aptitude for making an article of general use (a weapon, for instance) which was before made by each man for himself, there arises a tendency towards the differentiation of that individual into a maker of weapons. His companions (warriors and hunters all of them) severally wish to have the best weapons that can be made; and are therefore certain to offer strong inducements to this skilled individual to make weapons for them. He, on the other hand, having both an unusual faculty, and an unusual liking, for making weapons (the capacity and the desire for any occupation being commonly associated), is predisposed to fulfil these commissions on the offer of adequate rewards: especially as his love of distinction is also gratified. This first specialization of function, once commenced, tends ever to become more decided. On the side of the weapon-maker, continued practice gives increased skill—increased superiority to his products. On the side of his clients, cessation of practice entails decreased skill. Thus the influences that determine this division of labour grow stronger in both ways: this social movement tends ever to become more decided in the direction in which it was first set up; and the incipient heterogeneity is, on the average of cases, likely to become permanent for that generation, if no longer. Such a process, besides differentiating the social mass into two parts, the one monopolizing, or almost monopolizing, the performance of a certain function, and the other having lost the habit, and in some measure the power, of performing that function, has a tendency to initiate other differentiations. The advance described implies the introduction of barter: the maker of weapons has, on each occasion, to be paid in such other articles as he agrees to take in exchange. Now he will not habitually take in exchange one kind of article, but many kinds. He does not want mats only, or skins, or fishing-gear; but he wants all these; and on each occasion will bargain for the particular things he most needs. What follows? If among the members of the tribe there exist any slight differences of skill in the manufacture of these various things, as there are almost sure to do, the weapon-maker will take from each one the thing which that one excels in making: he will exchange for mats with him whose mats are superior, and will bargain for the fishing-gear of whoever has the best. But he who has bartered away his mats or his fishing-gear, must make other mats or fishing-gear for himself; and in so doing must, in some degree, further develop his aptitude. Thus it results that the small specialities of faculty possessed by various members of the tribe will tend to grow more decided. If such transactions are from time to time repeated, these specializations may become appreciable. And whether or not there ensue distinct differentiations of other individuals into makers of particular articles, it is clear that incipient differentiations take place throughout the tribe: the one original cause produces not only the first dual effect, but a number of secondary dual effects, like in kind but minor in degree. This process, of which traces may be seen among groups of school-boys, cannot well produce a lasting distribution of functions in an unsettled tribe; but where there grows up a fixed and multiplying community, such differentiations become permanent, and increase with each generation. An addition to the number of citizens, involving a greater demand for every commodity, intensifies the functional activity of each specialized person or class; and this renders the specialization more definite where it already exists, and establishes it where it is but nascent. By increasing the pressure on the means of subsistence, a larger population again augments these results; since every individual is forced more and more to confine himself to that which he can do best, and by which he can gain most. And this industrial progress, by aiding future production, opens the way for further growth of population, which reacts as before. Presently, under the same stimuli, new occupations arise. Competing workers, severally aiming to produce improved articles, occasionally discover better processes or better materials. In weapons and cutting-tools, the substitution of bronze for stone entails on him who first makes it, a great increase of demand—so great an increase that he presently finds all his time occupied in making the bronze for the articles he sells, and is obliged to depute the fashioning of these articles to others; and eventually the making of bronze, thus gradually differentiated from a pre-existing occupation, becomes an occupation by itself. But now mark the ramified changes which follow this change. Bronze soon replaces stone, not only in the articles it was first used for, but in many others; and so affects the manufacture of them. Further, it affects the processes which such improved utensils subserve, and the resulting products—modifies buildings, carvings, dress, personal decorations. Yet again, it sets going sundry manufactures which were before impossible, from lack of a material fit for the requisite tools. And all these changes react on the people—increase their manipulative skill, their intelligence, their comfort—refine their habits and tastes.

The only further fact demanding notice, is, that we here see more clearly than ever, that in proportion as the area over which any influence extends, becomes heterogeneous, the results are in a yet higher degree multiplied in number and kind. While among the primitive tribes to whom it was first known, caoutchouc caused but few changes, among ourselves the changes have been so many and varied that the history of them occupies a volume. Upon the small, homogeneous community inhabiting one of the Hebrides, the electric telegraph would produce, were it used, scarcely any results; but in England the results it produces are multitudinous.

Space permitting, the synthesis might here be pursued in relation to all the subtler products of social life. It might be shown how, in Science, an advance of one division presently advances other divisions—how Astronomy has been immensely forwarded by discoveries in Optics, while other optical discoveries have initiated Microscopic Anatomy, and greatly aided the growth of Physiology—how Chemistry has indirectly increased our knowledge of Electricity, Magnetism, Biology, Geology—how Electricity has reacted on Chemistry and Magnetism, developed our views of Light and Heat, and disclosed sundry laws of nervous action. In Literature the same truth might be exhibited in the still-multiplying forms of periodical publications that have descended from the first newspaper, and which have severally acted and reacted on other forms of literature and on each other; or in the bias given by each book of power to various subsequent books. The influence which a new school of Painting (as that of the pre-Raffaelites) exercises on other schools; the hints which all kinds of pictorial art are deriving from Photography; the complex results of new critical doctrines; might severally be dwelt on as displaying the like multiplication of effects. But it would needlessly tax the reader’s patience to detail, in their many ramifications, these various changes: here become so involved and subtle as to be followed with some difficulty.

§ 162. After the argument which closed the last chapter, a parallel one seems here scarcely required. For symmetry’s sake, however, it will be proper briefly to point out how the multiplication of effects, like the instability of the homogeneous, is a corollary from the persistence of force.

Things which we call different are things which react in different ways; and we can know them as different only by the differences in their reactions. When we distinguish bodies as hard and soft, rough and smooth, we simply mean that certain like muscular forces expended on them are followed by unlike sets of sensations—unlike reactive forces. Objects that are classed as red, blue, yellow, &c., are objects that decompose light in strongly-contrasted ways; that is, we know contrasts of colour as contrasts in the changes produced in a uniform incident force. Manifestly, any two things which do not work unequal effects on consciousness, either by unequally opposing our own energies, or by impressing our senses with unequally modified forms of certain external energies, cannot be distinguished by us. Hence the proposition that the different parts of any whole must react differently on a uniform incident force, and must so reduce it to a group of multiform forces, is in essence a truism. A further step will reduce this truism to its lowest terms.

When, from unlikeness between the effects they produce on consciousness, we predicate unlikeness between two objects, what is our warrant? and what do we mean by the unlikeness, objectively considered? Our warrant is the persistence of force. Some kind or amount of change has been wrought in us by the one, which has not been wrought by the other. This change we ascribe to some force exercised by the one which the other has not exercised. And we have no alternative but to do this, or to assert that the change had no antecedent; which is to deny the persistence of force. Whence it is further manifest that what we regard as the objective unlikeness is the presence in the one of some force, or set of forces, not present in the other—something in the kinds or amounts or directions of the constituent forces of the one, which those of the other do not parallel. But now if things or parts of things which we call different, are those of which the constituent forces differ in one or more respects; what must happen to any like forces, or any uniform force, falling on them? Such like forces, or parts of a uniform force, must be differently modified. The force which is present in the one and not in the other, must be an element in the conflict—must produce its equivalent reaction; and must so affect the total reaction. To say otherwise is to say that this differential force will produce no effect; which is to say that force is not persistent.

I need not develop this corollary further. It manifestly follows that a uniform force, falling on a uniform aggregate, must undergo dispersion; that falling on an aggregate made up of unlike parts, it must undergo dispersion from each part, as well as qualitative differentiations; that in proportion as the parts are unlike, these qualitative differentiations must be marked; that in proportion to the number of the parts, they must be numerous; that the secondary forces so produced, must undergo further transformations while working equivalent transformations in the parts that change them; and similarly with the forces they generate. Thus the conclusions that a part-cause of Evolution is the multiplication of effects; and that this increases in geometrical progression as the heterogeneity becomes greater; are not only to be established inductively, but are deducible from the deepest of all truths

[]Had this paragraph, first published in the Westminster Review in 1857, been written after the appearance of Mr. Darwin’s work on The Origin of Species, it would doubtless have been otherwise expressed. Reference would have been made to the process of “natural selection,” as greatly facilitating the differentiations described. As it is, however, I prefer to let the passage stand in its original shape: partly because it seems to me that these successive changes of conditions would produce divergent varieties or species, apart from the influence of “natural selection” (though in less numerous ways as well as less rapidly); and partly because I conceive that in the absence of these successive changes of conditions, “natural selection” would effect comparatively little. Let me add that though these positions are not enunciated in The Origin of Species, yet a common friend gives me reason to think that Mr. Darwin would coincide in them; if he did not indeed consider them as tacitly implied in his work.