No single piece of organic mechanism is oftener or more confidently appealed to by Theists as rendering conclusive evidence on their side than the eye, nor would they run much risk by allowing sentence to go for or against them according as Mr. Darwin has or has not succeeded in his attempt to explain that evidence away. Possibly he may disclaim having made any attempt of the kind, and I must admit that it is less by what he says than by what he leaves unsaid, that he lays himself open to the charge. Indeed, in almost all he says on the subject, I myself cordially agree, embracing even some of his views with less of hesitation than he seems to have felt in putting them forward. He seems to me, for instance, to have somewhat gratuitously admitted it to be apparently 'in the highest degree absurd to suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection.' For since, as he proceeds unanswerably to argue, 'numerous gradations, from an imperfect and simple eye to one perfect and complex, each grade being useful to its possessor, can certainly be shown to exist;' since, as certainly, slight variations of the eye do occur, and are inherited, and since of these variations there cannot but be some which are useful to the animal exhibiting them under changing conditions of life, the difficulty of believing in the formation of a perfect and complex eye by natural selection can be little else than a prejudice of the imagination. He proceeds to indicate some probable stages in the assumed process. Some of the lowest organisms, in which no trace of nerves can be detected, are known to be sensible to light, owing, probably, to the presence in the sarcode of which they are mainly composed, of certain elements which, in organisms somewhat higher in the scale, become aggregated and developed into nerves specially endowed with the same sensibility. An optic nerve thus formed, surrounded by pigment cells, and covered by translucent skin, is the simplest organ that can be called an eye, but it is an eye incapable of distinct vision, and serving only to distinguish light from darkness. In certain star-fishes, small depressions in the layer of pigment-cells are filled with transparent gelatinous matter projecting with a convex surface like a rudimentary cornea, and this, it has been suggested, may serve, not only to form an image, but to concentrate the luminous rays. In insects, the numerous facets in the cornea of their great compound eyes have now been ascertained to form true lenses, the cones, moreover, having been discovered to include curiously modified nervous filaments. It is impossible not, in this series of changes, to perceive the appearance of graduation, nor ought there to be much difficulty in believing the apparent graduation to be real, when we consider how few comparatively are the still living forms in which the changes cited have been observed, and how far more numerous the extinct forms by which intermediate changes may have been presented. If there be no extravagance in supposing that natural selection may have occasioned these early steps, neither is there any in supposing that, by continued progress in the same direction, it may at length have fabricated the most perfect optical instrument possessed by any member of the articulata. And, if credited so far, why not still further? why not with competence to form a man's or an eagle's eye? So far I am as completely at one with Mr. Darwin in respect to the eye as in respect to any other of the subjects taken by him for illustration. The fact is, however, that in this, as in every similar instance, he has completely evaded the real difficulties of the case. It is not a whit more startling to be told that the most complex eye, with all the latest improvements, than to be told that the earliest rudiment of an optic nerve, may have been formed by the gradual accumulation of minute differences. Only allow time enough for the requisite accumulation, and neither operation is one whit more unintelligible than the other. The difficulty, equally and utterly insuperable in both cases, is to understand how the difference can have been undesigned. 'How a nerve comes to be sensitive to light,' says Mr. Darwin, 'hardly concerns us more than how life itself originated.' Perhaps not; nor, indeed, very well could it, for the second question of the two is surely one of almost unsurpassed concernment; but, at any rate, when either of the two is asked, nothing can be more reprehensible than, by studiously ignoring the only alternative reply, to leave it to be inferred that the nerve made itself, or that life caused itself to live, that both are in short examples of what Mr. Darwin strangely calls 'variation causing alterations.'[41] Let us briefly consider a few of the results supposed to be attributable to this singular process. The eye, as every reader of course knows, though here and there one perhaps may not be the worse for being reminded, consists of four coats—the sclerotic, outermost and strongest, which constitutes the white of the eye; the circular, tough, and coloured, yet pellucid, cornea, in the centre of which is seen the pupil; the choroid, full charged with black pigment, and lining the sclerotic; the retina, an expansion of the optic nerve, lining in its turn the choroid; of the iris, a flat membrane, dividing the eye into two very unequally-sized chambers; of a lens termed the crystalline, suspended in the posterior chamber immediately behind the iris; and of two humours (also virtual lenses), whereof one, the aqueous, is enclosed in the anterior chamber formed by the iris and the cornea, while the other, the vitreous, fills the whole of the posterior chamber save what is occupied by the crystalline lens. By what nice interlacement of filaments the fibrous ring that margins the pupil, or aperture through the iris, regulates the admission of light, contracting or expanding, yet always preserving its circular form, according as the brilliance is excessive or deficient; how the humours or lenses are continually varying in figure and relative position so as to concentrate every pencil of light admitted on that point exactly where the retina is spread out to receive it; how, according as the object looked at is near at hand or far off, certain muscles perform quite opposite services, rendering the cornea more or less prominent, pushing the crystalline lens forward or backward, and thereby lengthening or shortening the axis of vision, so that, whether the rays enter divergently from a near object, or parallel from a remote one, they equally fall into focus at the same distance beyond, and equally form on the retina a picture of the object from which they come, perhaps compressing a landscape of five or six square leagues into a space of half an inch diameter, and anon allowing the page of a book or a dinner-plate to occupy the entire field of vision—to these and to any kindred marvels it would be superfluous more than momentarily to refer. Suffice it to note how measureless the superiority, as a mere piece of mechanism, of an average eye to the finest of telescopes, and how just, nevertheless, is the telescope-maker's claim to praise for skilful adaptation to the laws of optics, when he has succeeded in a faint and feeble imitation of some minor part of nature's visual apparatus. Yet nature's original and infinitely more beautiful aptitudes we are forbidden to deem adaptations, being required instead to regard them as self-produced, or, at any rate, as having been undesigned. Now I unreservedly admit that, among all conceivable forms, among the most exquisitely beautiful and most usefully intricate and complex, there is not one which may not possibly have been produced without aim or purpose by the mere restlessness of elemental forces; the amount of probability of their having been so produced being, however, according to the formula already set forth in its proper place, as one to infinity multiplied more or less frequently by itself. But what adequate superlative shall we invent to express the credulity, the credulosity run mad, of those who, in a matter of scientific belief, deliberately accept such odds. Observe how at once extravagantly gratuitous and painfully elaborate such credulosity is; how easily, on the one hand, all its ends could be served by the simple expedient of supposing a superintending intelligence; how, on the other, it compels ingenuity like Mr. Darwin's to entrench itself behind a phrase of utterly unmeaning gibberish.
If you see a man moving slowly, with head down, over an extensive plain, you may fairly suspect that he does not know where he is going, and possibly does not mean to go anywhere in particular. But if you perceive that on reaching a ditch he takes a leap over, you are quite sure that, when leaping, he meant to get to the other side. To that extent his saltatory movement is unequivocal evidence of design. It is perhaps to escape the necessity of a similar inference that Mr. Darwin so frequently quotes the proverb Natura non facit saltum; but, if so, he leans on a broken reed—on a bit of proverbial philosophy as weak as the weakest of Mr. Tupper's. That Nature does sometimes make a leap, and a pretty long one, must be obvious to any visitor to the Museum of the London College of Surgeons, who has examined the two-headed and four-legged human fœti there preserved in spirits. It may be said that these are leaps in the wrong direction. Be it so. Still, whoever can leap backward can make an equal leap forward, and most people will find the latter the easier feat of the two. The power, whatever it be, that coupled together the Siamese Twins, and gave to those respected brothers, the late William and Robert Chambers of Edinburgh, twelve fingers and twelve toes apiece, would not have gone at all more out of the way by doing, suddenly and at once, several of those things which Mr. Darwin doubts not that it does slowly and by degrees—by single acts, for instance, instead of by a succession of acts, aggregating into the semblance of an optic nerve certain elements in the sarcode of certain low organisms, spreading out the nerve thus formed into a network or retina, forming a number of separate pigment-cells into a homogeneous cornea, and following up these first steps by others which, how much soever more apparently complex, would cost comparatively little after the earlier and simpler ones had been taken. Now let but the power competent to do these things be credited with sense enough to be aware of its competence, and it may then be regarded as not unlikely to have done some of them on purpose. Whereupon, the genesis of the eye ceases to be a mystery. All the appearances of contrivance that have resulted from the operation find their obvious and complete explanation in the assumption of a contriver, and all such hazy films as that of variability producing variation cease to be capable of serving as excuses for wilful blindness. And why should not the power in question be so credited? Here is Mr. Darwin's solitary reason why. He doubts whether the inference implied may not be 'presumptuous.' He apprehends that we have no 'right to assume that the Creator works by intellectual powers like those of a man.' Truly, of all suggested modes of marking respect for creative power, that of assuming it to have worked unintelligently is the most original.
The hypothesis offered by Mr. Darwin in explanation of the most perfect of organic structures, is deemed by him to be equally explanatory of the most marvellous of animal instincts. Parenthetically, here, never having as yet met with a definition of instinct which I am able to accept as satisfactory, I make bold to offer a description of my own. Instinct is innate knowledge how to perform any useful actions, accompanied by a tendency or propensity to perform those actions, but wholly unaccompanied by knowledge of any purpose which they can serve. This is pure instinct, an example whereof is afforded by the beaver, of which animal I have somewhere read that one caught when newly born, and brought up by itself in a room in its captor's house, proceeded after a while to build up across the apartment the semblance of a dam, composed of brushes, rugs, billets of wood, and other litter. Pure instinct differs essentially, not in degree only, but in kind, from reason, which is not knowledge, but an instrument for acquiring knowledge. Instinct, however, is rarely if ever found pure, being apparently always accompanied by more or less of reason. Even a polype makes some show of reason by moving its cilia in one mode when it desires to suck in food, and in another when it merely wishes to move on; while it is scarcely possible for an unprejudiced spectator to doubt of its being by a rational deduction from experience that a dog knows that it will get kicked if it presume to snatch at the meat on its master's plate, instead of waiting for the scraps he may be pleased to throw to it when he has done. Instinct by necessary implication involves habit; habit as necessarily always more or less modifies structure; structural modification always may be, and often is, inherited, carrying with it a tendency to the habit out of which itself arose; therefore habit and instinct are likewise heritable. Some instincts are originated artificially. The reason why, on the very first opportunity, a young pointer has been known to point at game, and a young sheep-dog to run round, instead of at, a flock of sheep, is that some of their respective ancestors had been carefully trained so to point and to wheel. These, however, are exceptions to the general rule. Most instincts are of what every one would call natural, and Mr. Darwin calls 'spontaneous' origin, he explaining the meaning of the latter term to be that the slight variations from a primordial type, the accumulation of which is considered by him to constitute actual instinct, are 'variations produced by the same unknown causes as those which produce slight deviations of bodily structure.' But here I am once more compelled to join issue with him. Of the causes which he styles unknown, I maintain that we know at least thus much—either they are themselves intelligent forces, or they are forces acting under intelligent direction; and in support of this proposition I need not perhaps do more than show from Mr. Darwin's example what infinitely harder things must be accepted by those who decline to accept this.
Mr. Darwin, like every really truth-loving controversialist, far from desiring to shroud, invites special attention to any seeming weaknesses in his position; and, therefore, when contending that all the faculties commonly classed as instincts, are exclusively due to natural selection, of course takes care to particularise the cellmaking faculty of the hive bee. And here, again, I gladly bear my humble testimony to the partial success he has achieved. Although bound to protest against the claim set up by him, on behalf of natural selection, to the entire credit of producing the hive bee's most remarkable characteristic, I cannot but think he has succeeded in removing all the apparent difficulties of believing that natural selection's share may have been not less important in that than in any other productive operation in which it takes part.
In popular estimation the hive bee is a heaven-born mathematician which, having been set the problem how to fill a given space with waxen cells with the least loss of room and expenditure of material, arrives by intuition and instantaneously at a solution which Newton himself was ignorant of, and to which, but for his discovery of the fluxional calculus, it would have been impossible for his follower, Maclaurin, to attain. And, doubtless, it may excusably be deemed supernatural that the insect should adopt off-hand precisely that six-sided figure, and precisely that inclination of the angles of the same figure's pyramidal roof or floor, which, only by very refined and recondite investigation, can be scientifically shown to be those best fitted for the purpose. Mr. Darwin has, however, adduced strong grounds for supposing the amazing architectural skill thus displayed to have been acquired, not suddenly, but by the same slow degrees as those which are so clearly traceable throughout organic progress in general. At the lower end of a short apiary series, he observed humble bees using their old cocoons for honey pots, sometimes adding to them short tubes of wax, and likewise making separate and very irregular cells entirely of wax. At the higher end of the series, he saw hive bees making double layers of cells, each cell an hexagonal prism with the basal ends of its six sides bevelled so as to fit on to a pyramid formed of three rhombs, and each of the three rhombs which compose the pyramidal base of a single cell on one side of the comb entering into the composition of one of the three adjoining cells on the opposite side. Intermediately, he found the Mexican meliponæ domesticæ depositing their honey in cells nearly spherical, and of nearly equal sizes. 'These cells, although aggregated into a mass otherwise irregular, are always at such a degree of nearness to each other that they would have intersected or broken into each other if the spheres had been completed. But this is never permitted, the bees building perfectly flat walls of wax between the spheres which thus tend to intersect. Hence, each cell consists of an outer spherical portion, and of two, three, or more, perfectly flat surfaces, according as the cell adjoins two, three, or more cells; and when one cell rests on three others, as from the spheres being nearly of the same size is very frequently and necessarily the case, the three flat surfaces are united into a pyramid rudely resembling the three-sided pyramidal base of the hive bee's cell, and necessarily enter, like the three rhombs of the latter, into the construction of three adjoining cells.' Reflecting on these remarkable gradations, it occurred to Mr. Darwin that if the melipona were to make its spheres of precisely equal sizes, and to arrange them symmetrically in double layers, and were further so to dispose them as that the centre of each should be at the distance of radius × √2 or radius × 1.41421 from the centres of the six surrounding spheres in the same layer, and at the same distance from the centres of the adjoining spheres in the other and parallel layer—then 'if planes of intersection between the several spheres on both layers were formed, there would result a double layer of hexagonal prisms united together by pyramidal bases formed of three rhombs; and the rhombs and the sides of the hexagonal prisms would have every angle identically the same with the best measurements that have been made of the cells of the hive bee.' Then, submitting this view to Professor Miller of Cambridge, he had the gratification of being assured by that distinguished geometer that it was strictly correct. Certainly a very happy example of an ingenious conjecture verified by a species of demonstration hardly inferior to the experimental. Certainly a very valuable testimony to the soundness of all the main and really essential principles of Darwinism. Good cause, certainly, is hereby shown for believing that the cell-making faculty of the hive bee may be nothing more than the aggregate of many minute and successive improvements upon that of the melipona, and this, again, than a similar aggregate of improvements on that of the humble bee; and for believing further that hive bee and melipona may both be either descendants from the humble bee, or joint-descendants with it from some still earlier common progenitor. In order to believe this it suffices to believe that a bee which at one period made, like the humble bee, cells very unequally sized and irregularly rounded, came gradually, in the course of time, to make them as nearly equal in size and as nearly spherical as those of the melipona; and subsequently, during a further lapse of time, came to arrange them at the same distances from each other, and in double layers like those of the humble bee. To assume thus much requires no inordinate stretch of faith; and thus much being assumed, it is seen at once that the hive bee, requiring for its cells only about half as much wax as the humble bee does, and consequently only about half as much honey for the secretion of the requisite wax, would, in a struggle for existence, leave the humble bee so little chance that in all probability the two species would nowhere coexist, were it not for the special resource derived by the humble bee from possession of a trunk long enough to enter the nectaries of certain flowers, which the shorter trunk of the hive bee is unable to tap. But though there be no difficulty in assuming the improvements in question to have gradually taken place, and to have become aggregated in the manner supposed, there is, to my mind, an insuperable objection to supposing that successive generations of bees should have successively adopted the improvements without either having the sense to know what they were doing, or being prompted by some superior intelligence that did know. I will not be so superfluous as to exaggerate the difficulty. Passing over the earlier stages of the process, and confining myself to one or two of the later, I will content myself with showing how infinitesimally small, when magnified to the utmost, are the chances in favour of these having been passed through blindly. I will admit it to be possible that in a society of purely meliponish habits, there might, in virtue of one or other of those inscrutable causes classed under the general name of spontaneous variation, arise some two or three individuals with an innate propensity to make accurately spherical and equally sized cells; that these individuals, if either males or fertile females, and not sterile neuters, might help to generate others with the same propensity, these again generating others, and so on, until the greater part or the whole of the community became possessed of the same constructive aptitude. I will admit further that, in virtue of the same inscrutable causes, individuals, at first few, but gradually increasing in number, might similarly be born with the additional tendency to make cells at the same, and that the most appropriate, distance from all adjoining cells; and will freely acknowledge that the bees, modifying their previous mode of construction, as meliponæ necessarily would do under these altered circumstances, would construct a layer of cells similar in all respects to those on one side of the hive bee's comb, except that their bases would be flat instead of pyramidal. Further, I admit that the bases would become pyramidal in case the bees should set about constructing double instead of single layers of cells on the same principle. Not a little liberality is required for these admissions. For, in the first place, the fact of the bees having acquired the habit of making perfect and equally sized spheres would not of itself be of any obvious benefit either to individual bees or to the society at large: in order that it should enable material and labour to be saved it would have to be accompanied by the habit of making the cells at special distances from each other. And, in the second place, though some few individuals should present themselves with an innate tendency to choose these special distances, whatever advantage might result therefrom, whatever saving of material or labour, would be shared in equally by the whole community, the particular individuals to whom it was due benefiting by it no more than any of the rest, and not being, in consequence, more likely than they to survive in any struggle for existence, or to leave behind them offspring inheriting their special characteristics. No help, therefore, can be derived from Mr. Darwin's principles towards conjecturing why a small minority of such specially endowed bees should be gradually converted into a majority, and should eventually constitute the whole community, thereupon becoming in fact converted into a new species. Let us, however, liberally waive this and all similar objections, and assume a community of hive bees to have been, in the utterly unaccountable manner indicated by the term spontaneous variation, developed from a meliponish stock. Unfortunately, all our liberality will be found to have been thrown away without perceptibly simplifying the problem to be solved. For, whatever be among meliponæ the distribution of the generative capacities, among hive bees, at any rate, all workers are sterile neuters, which never have any offspring to whom to bequeath their cellmaking skill, while the queen bee and drones, which alone can become parents, have no such skill to bequeath. Clearly the formula of 'descent with modification by natural selection,' is, in its literal sense, utterly inapplicable here. In whatever manner the cell-making faculty might have been acquired by the first homogeneous swarm of hive bees, it must inevitably have terminated with the generation with which it commenced, if transmission by direct descent had been necessary for its continuance. The only resource open to Mr. Darwin is to suppose, not merely (what is, indeed, obviously the fact) that queen bee after queen bee, besides generating each in turn a progeny of workers endowed with instincts which their parents did not possess and could not therefore impart, generated also princess bees destined in due season to generate a working progeny similarly endowed with instincts underived from their parents; but to suppose further that all this has happened in the total absence of aim, object, intention, or design. Now that all this should have so happened, although not absolutely inconceivable, nor, therefore, absolutely impossible, is surely too incredible to be believed except in despair of some other hypothesis a trifle less preposterous. It is surely not worth while to set the doctrine of probabilities so completely at naught, for the sake of an explanation which avowedly leaves every difficulty unexplained, referring them all to causes not simply unknown but unconjecturable. What excuse, then, have philosophers, of all people, for doing this in preference to the simple expedient of supposing that, although the parturient bee, queen or other, cannot intend that any of her progeny should be more bounteously endowed than herself, there is an independent intelligence that does so intend? To content oneself with pronouncing such preference to be eminently unscientific is tenderness of language nearly akin, I fear, to literary bathos.
III.
I have said that the form of unbelief to which, on the principle of calling a spade a spade, I have taken the liberty of giving the name of Scientific Atheism, manifests itself now-a-days rather by ignoration than by formal denial of God. This, however, is not a new feature in any atheism really worthy of being styled scientific. Even as Mr. Darwin verbally recognises a Creator, although without assigning to Him any share in creation, even so Kant, when more than a century ago undertaking, in his 'General Natural History and Theory of the Celestial Bodies,'[42] to account for the constitution and mechanical origin of the universe on Newtonian principles, spoke of the elements as deriving their essential qualities from the 'eternal thought of the Divine Intelligence,' without, however, crediting the said Intelligence with having interposed in order to carry out His thoughts. 'Give me matter,' he says, 'and I will build the world;' and without other data than diffused atoms of matter endowed with simple attractive and repulsive forces, he proceeds to expound a complete cosmogony.
He pictures to himself the universe as originally an infinite expansion of minutely subdivided matter, and supposing a single centre of attraction to be somewhere therein set up, he endeavours to show that the result must be a prodigious central body surrounded by systems of solar and planetary worlds in all stages of development. 'In vivid language,' says Professor Huxley,[43] 'he describes the great world-maelstrom widening the margin of its prodigious eddy in the slow progress of millions of ages, gradually reclaiming more and more of the molecular waste, and converting chaos into cosmos.' Then, fixing his attention more particularly on our own system, he accounts for the relation between the masses and densities of the planets and their distances from the sun, for the eccentricity of their orbits, for their rotation, for their satellites, for the general agreement in the direction of rotation among the celestial bodies, for Saturn's ring, and for the zodiacal light. All this he does, according to Professor Huxley, by 'strict deduction from admitted dynamical principles,' and I, well aware of my own inability to form an independent judgment on the point, gladly take so high an authority's word for it. For aught that I know, Kant's attractive and repulsive forces being admitted, the establishment of centres of attraction, and of circle within circle of revolutions round them, and all his other details, would follow naturally and of course. I limit myself to asking, Whence these simple forces?—and when Kant replies, 'From the Eternal Thought of the Divine Understanding,' I should be the last to criticise if his answer stopped there. Unfortunately, he adds that the forces were 'evolved without purpose'; in other words, that the Intelligence which thought them into existence failed to think of any purpose for them. 'Matter,' he proceeds, 'is purely passive, yet, nevertheless, has in its simplest state a determination towards the assumption of a more perfect constitution in the way of natural development, whereby it breaks up rest, stirs up nature, gives to chaos shape.' For the elements whereof this passively stirring up matter is composed 'have native powers of setting each other in motion, and are to themselves a spring of life;' and when, having of course being previously dead, they have given themselves life, they forthwith begin to attract each other with a strength varying with their varying degrees of specific gravity. The scattered elements of the denser sort collect by attraction all particles of less specific gravity out of their immediate neighbourhood, and are themselves similarly collected by particles of still denser sort, these again by others denser yet, and so on, until, as results of this particular action, several masses are formed which in like manner would converge towards and be united with the largest and densest of their number, were it not that the counter principle of repulsion now comes into play. This principle—familiarly exemplified in the elasticity of vapours, the emanations from strong smelling substances, and the expansion of all spirituous substances—causes the vertical movements of the converging masses to be deflected laterally, so as ultimately to enclose the central mass within circles which, at first intersecting each other in all directions, are at length, by dint of mutual collision, made all to revolve in the same direction, and nearly the same plane.
Now I most earnestly protest against being suspected of what in me would be the intolerable impertinence of desiring to cast ridicule on these magnificent speculations, the grandeur of which I thoroughly appreciate so far as my scant mathematics enable me to follow them. I take exception to them only because the language in which they are couched seems to imply that operations, of whose nature one of the most powerful of human intellects could, at its utmost stretch, catch only a faint hazy inkling, may yet have been initiated and perfected without the intervention of any intellect at all. This is a falsism against which my respect for philosophy and philosophers makes me only all the more indignant when I find any of the latter falling into it, as those of them inevitably must who, busying themselves, early or late,
With a mighty debate,
A profound speculation about the creation
And organical life, and chaotical strife,
With various notions of heavenly motions,
And rivers and oceans, and valleys and mountains,
And sources of fountains, and meteors on high,
And stars in the sky,—propose by and bye,