THIS world of ours has, on the whole, been an inclement region for the growth of natural truth; but it may be that the plant is all the hardier for the bendings and buffetings it has undergone. The torturing of a shrub, within certain limits, strengthens it Through the struggles and pa.s.sions of the brute, man reaches his estate; through savagery and barbarism his civilisation; and through illusion and persecution his knowledge of nature, including that of his own frame. The bias towards natural truth must have been strong to have withstood and overcome the opposing forces. Feeling appeared in the world before Knowledge; and thoughts, conceptions, and creeds, founded on emotion, had, before the dawn of science, taken root in man. Such thoughts, conceptions, and creeds must have met a deep and general want; otherwise their growth could not have been so luxuriant, nor their abiding power so strong. This general need--this hunger for the ideal and wonderful--led eventually to the differentiation of a caste, whose vocation it was to cultivate the mystery of life and its surroundings, and to give shape, name, and habitation to the emotions which that mystery aroused. Even the savage lived, not by bread alone, but in a mental world peopled with forms answering to his capacities and needs. As time advanced--in other words, as the savage opened out into civilised man--these forms were purified and enn.o.bled until they finally emerged in the mythology and art of Greece:

Where still the magic robe of Poesy Wound itself lovingly around the Truth.

[Footnote:

Da der Dichtung zauberische Huelle Sich noch lieblich um die Wahrheit wand.'--Schiller.]

As poets, the priesthood would have been justified, their deities, celestial and otherwise, with all their retinue and appliances, being more or less legitimate symbols and personifications of the aspects of nature and the phases of the human soul. The priests, however, or those among them who were mechanics, and not poets, claimed objective validity for their conceptions, and tried to base upon external evidence that which sprang from the innermost need and nature of man.

It is against this objective rendering of the emotions--this thrusting into the region of fact and positive knowledge of conceptions essentially ideal and poetic--that science, consciously or unconsciously, wages war. Religious feeling is as much a verity as any other part of human consciousness; and against it, on its subjective side, the waves of science beat in vain. But when, manipulated by the constructive imagination, mixed with imperfect or inaccurate historic data, and moulded by misapplied logic, this feeling makes claims which traverse our knowledge of nature, science, as in duty bound, stands as a hostile power in its path. It is against the mythologic scenery, if I may use the term, rather than against the life and substance of religion, that Science enters her protest. Sooner or later among thinking people, that scenery will be taken for what it is worth--as an effort on the part of man to bring the mystery of life and nature within the range of his capacities; as a temporary and essentially fluxional rendering in terms of knowledge of that which transcends all knowledge, and admits only of ideal approach.

The signs of the times, I think, point in this direction. It is, for example, the obvious aim of Mr. Matthew Arnold to protect, amid the wreck of dogma, the poetic basis of religion. And it is to be remembered that under the circ.u.mstances poetry may be the purest accessible truth. In other influential quarters a similar spirit is at work. In a remarkable article published by Professor Knight of St.

Andrews in the September number of the 'Nineteenth Century,' amid other free utterances, we have this one: 'If matter is not eternal, its first emergence into being is a miracle beside which all others dwindle into absolute insignificance. But, as has often been pointed out, the process is unthinkable; the sudden apocalypse of a material world out of blank nonent.i.ty cannot be imagined; [Footnote: Professor Knight will have to reckon with the English Marriage Service, one of whose Collects begins thus: 'O G.o.d, who by thy mighty power halt made all things of nothing.] its emergence into order out of chaos when "without form and void" of life, is merely a poetic rendering of the doctrine of its slow evolution.' These are all bold words to be spoken before the moral philosophy cla.s.s of a Scotch university, while those I have underlined show a remarkable freedom of dealing with the sacred text. They repeat in terser language what I ventured to utter four years ago regarding the Book of Genesis. 'Profoundly interesting and indeed pathetic to me are those attempts of the opening mind of man to appease its hunger for a Cause. But the Book of Genesis has no voice in scientific questions. _It is a poem, not a scientific treatise._ In the former aspect it is for ever beautiful; in the latter it has been, and it will continue to be, purely obstructive and hurtful.' My agreement with Professor Knight extends still further. 'Does the vital,' he asks, 'proceed by a still remoter development from the non-vital? Or was it created by a fiat of volition? Or'--and here he emphasises his question--'has it always existed in some form or other as an eternal const.i.tuent of the universe? I do not see,' he replies, 'how we can escape from the last alternative.' With the whole force of my conviction I say, Nor do I, though our modes of regarding the 'eternal const.i.tuent' may not be the same.

When matter was defined by Descartes, he deliberately excluded the idea of force or motion from its attributes and from his definition.

Extension only was taken into account. And, inasmuch as the impotence of matter to generate motion was a.s.sumed, its observed motions were referred to an external cause. G.o.d, resident outside of matter, gave the impulse. In this connection the argument in Young's 'Night Thoughts' will occur to most readers:

Who Motion foreign to the smallest grain Shot through vast ma.s.ses of enormous weight?

Who bid brute Matter's restive lump a.s.sume Such various forms, and gave it wings to fly?

Against this notion of Descartes the great deist John Toland, whose ashes lie unmarked in Putney Churchyard, strenuously contended. He affirmed motion to be an inherent attribute of matter--that no portion of matter was at rest, and that even the most quiescent solids were animated by a motion of their ultimate particles. The success of his contention, according to the learned and laborious Dr. Berthold, [Footnote: 'John Toland und der Monismus der Gegenwart,' Heidelberg, Carl Winter.] ent.i.tles Toland to be regarded as the founder of that monistic doctrine which is now so rapidly spreading.

It seems to me that the idea of vitality entertained in our day by Professor Knight, closely resembles the idea of motion entertained by his opponents in Toland's day. Motion was then virtually a.s.serted to be a thing sui generis, distinct from matter, and incapable of being generated out of matter. Hence the obvious inference when matter was observed to move. It was the vehicle of an energy not its own--the repository of forces impressed on it from without--the purely pa.s.sive recipient of the shock of the Divine. The logical form continues, but the subject-matter is changed. 'The evolution of nature,' says Professor Knight, 'may be a fact; a daily and hourly apocalypse. But we have no evidence of the non-vital pa.s.sing into the vital.

Spontaneous generation is, as yet, an imaginative guess, unverified by scientific tests. And matter is not itself alive. Vitality, whether seen in a single cell of protoplasm or in the human brain, is a thing sui generis, distinct from matter, and incapable of being generated out of matter.' It may be, however, that, in process of time, vitality will follow the example of motion, and, after the necessary antecedent wrangling, take its place among the attributes of that 'universal mother' who has been so often misdefined.

That 'matter is not itself alive' Professor Knight seems to regard as an axiomatic truth. Let us place in contrast with this the notion entertained by the philosopher Ueberweg, one of the subtlest heads that Germany has produced. 'What occurs in the brain' says Ueberweg 'would, in my opinion, not be possible, if the process which here appears in its greatest concentration did not obtain generally, only in a vastly diminished degree. Take a pair of mice and a cask of flour. By copious nourishment the animals increase and multiply, and in the same proportion sensations and feelings augment. The quant.i.ty of these latter possessed by the first pair, is not simply diffused among their descendants, for in that case the last must feel more feebly than the first. The sensations and feelings must necessarily be referred back to the flour, where they exist, weak and pale it is true, and not concentrated as they are in the brain.' [Footnote: Letter to Lange: 'Geschichte des Materialismus,' zweite Aufl, vol. ii. p. 521.] We may not be able to taste or smell alcohol in a tub of fermented cherries, but by distillation we obtain from them concentrated Kirschwa.s.ser. Hence Ueberweg's comparison of the brain to a still, which concentrates the sensation and feeling, pre-existing, but diluted in the food.

'Definitions,' says Mr. Holyoake, [Footnote: 'Nineteenth Century,'

September 1878.] 'grow as the horizon of experience expands. They are not inventions, but descriptions of the state of a question. No man sees all through a discovery at once.' Thus Descartes's notion of matter, and his explanation of motion, would be put aside as trivial by a physiologist or a crystallographer of the present day. They are not descriptions of the state of the question. And yet a desire sometimes shows itself in distinguished quarters to bind us own to conceptions which pa.s.sed muster in the infancy of knowledge, but which are wholly incompatible with our present enlightenment. Mr.

Martineau, I think, errs when he seeks to hold me to views enunciated by 'Democritus and the mathematicians.' That definitions should change as knowledge advances is in accordance both with sound sense and scientific practice. When, for example, the undulatory theory was started, it was not imagined that the vibrations of light could be transverse to the direction of propagation. The example of sound was at hand, which was a case of longitudinal vibration. Now the subst.i.tution of transverse for longitudinal vibrations in the case of light involved a radical change of conception as to the mechanical properties of the luminiferous medium. But though this change went so far as to fill s.p.a.ce with a substance, possessing the properties of a solid, rather than those of a gas, the change was accepted, because the newly discovered facts imperatively demanded it. Following Mr.

Martineau's example, the opponent of the undulatory theory might effectually twit the holder of it on his change of front. 'This aether of yours,' he might say, 'alters its style with every change of service. Starting as a beggar, with scarce a rag of 'property' to cover its bones, it turns up as a prince when large undertakings are wanted. You had some show of reason when, with the case of sound before you, you a.s.sumed your aether to be a gas in the last extremity of attenuation. But now that new service is rendered necessary by new facts, you drop the beggar's rags, and accomplish an undertaking, great and princely enough in all conscience; for it implies that not only planets of enormous weight, but comets with hardly any weight at all, fly through your hypothetical solid without perceptible loss of motion.' This would sound very cogent, but it would be very vain.

Equally vain, in my opinion, is Mr. Martineau's contention that we are not justified in modifying, in accordance with advancing knowledge, our notions of matter.

Before parting from Professor Knight, let me commend his courage as well as his insight. We have heard much of late of the peril to morality involved in the decay of religious belief. What Mr. Knight says under this head is worthy of all respect and attention. 'I admit,' he writes, 'that were it proved that the moral faculty was derived as well as developed, its present decisions would not be invalidated. The child of experience has a father whose teachings are grave, peremptory, and august; and an earthborn rule may be as stringent as any derived from a celestial source. It does not even follow that a belief in the material origin of spiritual existence, accompanied by a corresponding decay of belief in immortality, must necessarily lead to a relaxation of the moral fibre of the race.

[Footnote: Is this really certain? Instead of standing in the relation of cause and effect, may not the 'decay' and 'relaxation' be merely coexistent, both, perhaps, flowing from common historic antecedents?] It is certain that it has often done so. But it is equally certain that there have been individuals, and great historical communities, in which the absence of the latter belief has neither weakened moral earnestness, nor prevented devotional fervour.' I have elsewhere stated that some of the best men of my acquaintance--men lofty in thought and beneficent in act--belong to a cla.s.s who a.s.siduously let the belief referred to alone. They derive from it neither stimulus nor inspiration, while--I say it with regret--were I in quest of persons who, in regard to the finer endowments of human character, are to be ranked with the unendowed, I should find some characteristic samples among the noisier defenders of the orthodox belief. These, however, are but 'hand-specimens' on both sides; the wider data referred to by Professor Knight const.i.tute, therefore, a welcome corroboration of my experience. Again, my excellent critic, Professor Blackie, describes Buddha as being 'a great deal more than a prophet; a rare, exceptional, and altogether transcendental incarnation of moral perfection.' [Footnote: 'Natural History of Atheism,' p. 136.] And yet, 'what Buddha preached was a gospel of pure human ethics, divorced not only from Brahma and the Brahminic Trinity, but even from the existence of G.o.d.' [Footnote: Natural History of Atheism,' p. 125.] These civilised and gallant voices from the North contrast pleasantly with the barbarous whoops which sometimes come to us along the same meridian.

Looking backwards from my present standpoint over the earnest past, a boyhood fond of play and physical action, but averse to schoolwork, lies before me. The aversion did not arise from intellectual apathy or want of appet.i.te for knowledge, but simply from the fact that my earliest teachers lacked the power of imparting vitality to what they taught. Athwart all play and amus.e.m.e.nt, however, a thread of seriousness ran through my character; and many a sleepless night of my childhood has been pa.s.sed, fretted by the question 'Who made G.o.d?' I was well versed in Scripture; for I loved the Bible, and was prompted by that love to commit large portions of it to memory. Later on I became adroit in turning my Scriptural knowledge against the Church of Rome, but the characteristic doctrines of that Church marked only for a time the limits of enquiry. The eternal Sonship of Christ, for example, as enunciated in the Athanasian Creed, perplexed me. The resurrection of the body was also a thorn in my mind, and here I remember that a pa.s.sage in Blair's 'Grave' gave me momentary rest.

Sure the same power That rear'd the piece at first and took it down Can rea.s.semble the loose, scatter'd parts And put them as they were.

The conclusion seemed for the moment entirely fair, but with further thought, my difficulties came back to me. I had seen cows and sheep browsing upon churchyard gra.s.s, which sprang from the decaying mould of dead men. The flesh of these animals was undoubtedly a modification of human flesh, and the persons who fed upon them were as undoubtedly, in part, a more remote modification of the same substance. I figured the self-same molecules as belonging first to one body and afterwards to a different one, and I asked myself how two bodies so related could possibly arrange their claims at the day of resurrection. The scattered parts of each were to be rea.s.sembled and set as they were. But if handed over to the one, how could they possibly enter into the composition of the other? Omnipotence itself, I concluded, could not reconcile the contradiction. Thus the plank which Blair's mechanical theory of the resurrection brought momentarily into sight, disappeared, and I was again cast abroad on the waste ocean of speculation.

At the same time I could by no means get rid of the idea that the aspects of nature and the consciousness of man implied the operation of a power altogether beyond my grasp--an energy the thought of which raised the temperature of the mind, though it refused to accept shape, personal or otherwise, from the intellect. Perhaps the able critics of the 'Sat.u.r.day Review' are justified in speaking as they sometimes do of Mr. Carlyle. They owe him nothing, and have a right to announce the fact in their own way. I, however, owe him a great deal, and am also in honour bound to acknowledge the debt. Few, perhaps, who are privileged to come into contact with that ill.u.s.trious man have shown him a st.u.r.dier front than I have, or in discussing modern science have more frequently withstood him. But I could see that his contention at bottom always was that the human soul has claims and yearnings which physical science cannot satisfy. England to come will a.s.suredly thank him for his affirmation of the ethical and ideal side of human nature.

Be this as it may, at the period now reached in my story the feeling referred to was indefinitely strengthened, my whole life being at the same time rendered more earnest, resolute, and laborious by the writings of Carlyle. Others also ministered to this result. Emerson kindled me, while Fichte powerfully stirred my moral pulse. [Footnote: The reader will find in the Seventeenth Lecture of Fichte's course on the 'Characteristics of the Present Age' a sample of the vital power of this philosopher.] In this relation I cared little for political theories or philosophic systems, but a great deal for the propagated life and strength of pure and powerful minds. In my later school-days, under a clever teacher, some knowledge of mathematics and physics had been picked up: my stock of both was, however, scanty, and I resolved to augment it. But it was really with the view of learning whether mathematics and physics could help me in other spheres, rather than with the desire of acquiring distinction in either science, that I ventured, in 1848, to break the continuity of my life, and devote the meagre funds then at my disposal to the study of science in Germany.

But science soon fascinated me on its own account. To carry it duly and honestly out, moral qualities were incessantly invoked. There was no room allowed for insincerity--no room even for carelessness. The edifice of science had been raised by men who had unswervingly followed the truth as it is in nature; and in doing so had often sacrificed interests which are usually potent in this world. Among these rationalistic men of Germany I found conscientiousness in work as much insisted on as it could be among theologians. And why, since they had not the rewards or penalties of the theologian to offer to their disciples? Because they a.s.sumed, and were justified in a.s.suming, that those whom they addressed had that within them which would respond to their appeal. If Germany should ever change for something less n.o.ble the simple earnestness and fidelity to duty, which in those days characterised her teachers, and through them her sons generally, it will not be because of rationalism. Such a decadent Germany might coexist with the most rampant rationalism without their standing to each other in the relation of cause and effect.

My first really laborious investigation, conducted jointly with my friend Professor k.n.o.blauch, landed me in a region which harmonised with my speculative tastes. It was essentially an enquiry in molecular physics, having reference to the curious, and then perplexing, phenomena exhibited by crystals when freely suspended in the magnetic field. I here lived amid the most complex operations of magnetism in its twofold aspect of an attractive and a repellent force. Iron was attracted by a magnet, bis.m.u.th was repelled, and the crystals operated on ranged themselves under these two heads. Faraday and Pluecker had worked a.s.siduously at the subject, and had invoked the aid of new forces to account for the phenomena. It was soon, however, found that the displacement in a crystal of an atom of the iron cla.s.s by an atom of the bis.m.u.th cla.s.s, involving no change of crystalline form, produced a complete reversal of the phenomena. The lines through the crystal which were in the one case drawn towards the poles of the magnet, were driven, in the other case, from these poles.

By such instances and the reasoning which they suggested, magne-crystallic action was proved to be due, not to the operation of new forces, but to the modification of the old ones by molecular arrangement. Whether diamagnetism, like magnetism, was a polar force, was in those days a subject of the most lively contention. It was finally proved to be so; and the most complicated cases of magne-crystallic action were immediately shown to be simple mechanical consequences of the principle of diamagnetic polarity. These early researches, which occupied in all five years of my life, and throughout which the molecular architecture of crystals was an incessant subject of mental contemplation, gave a tinge and bias to my subsequent scientific thought, and their influence is easily traced in my subsequent enquiries. For example, during nine years of labour on the subject of radiation, heat and light were handled throughout by me, not as ends, but as instruments by the aid of which the mind might perchance lay hold upon the ultimate particles of matter.

Scientific progress depends mainly upon two factors which incessantly interact--the strengthening of the mind by exercise, and the illumination of phenomena by knowledge. There seems no limit to the insight regarding physical processes which this interaction carries in its train. Through such insight we are enabled to enter and explore that subsensible world into which all natural phenomena strike their roots, and from which they derive nutrition. By it we are enabled to place before the mind's eye atoms and atomic motions which lie far beyond the range of the senses, and to apply to them reasoning as stringent as that applied by the mechanician to the motions and collisions of sensible ma.s.ses. But once committed to such conceptions, there is a risk of being irresistibly led beyond the bounds of inorganic nature. Even in those early stages of scientific growth, I found myself more and more compelled to regard not only crystals, but organic structures, the body of man inclusive, as cases of molecular architecture, infinitely more complex, it is true, than those of inorganic nature, but reducible, in the long run, to the same mechanical laws. In ancient journals I find recorded ponderings and speculations relating to these subjects, and attempts made, by reference to magnetic and crystalline phenomena, to present some satisfactory image to the mind of the way in which plants and animals are built up. Perhaps I may be excused for noting a sample of these early speculations, already possibly known to a few of my readers, but which here finds a more suitable place than that which it formerly occupied.

Sitting, in the summer of 1855, with my friend Dr. Rebus under the shadow of a ma.s.sive elm on the bank of a river in Normandy, the current of our thoughts and conversation was substantially this: We regarded the tree above us. In opposition to gravity its molecules had ascended, diverged into branches, and budded into innumerable leaves. What caused them to do so--a power external to themselves, or an inherent force? Science rejects the outside builder; let us, therefore, consider from the other point of view the experience of the present year. A low temperature had kept back for weeks the life of the vegetable world. But at length the sun gained power--or, rather, the cloud-screen which our atmosphere had drawn between him and us was removed--and life immediately kindled under his warmth. But what is life, and how can solar light and heat thus affect it? Near our elm was a silver birch, with its leaves rapidly quivering in the morning air. We had here motion, but not the motion of life. Each leaf moved as a ma.s.s under the influence of an outside force, while the motion of life was inherent and molecular. How are we to figure this molecular motion--the forces which it implies, and the results which flow from them? Suppose the leaves to be shaken from the tree and enabled to attract and repel each other. To fix the ideas, suppose the point of each leaf to repel all the other points and to attract the roots, and the root of each leaf to repel all other roots, but to attract the points. The leaves would then resemble an a.s.semblage of little magnets abandoned freely to the interaction of their own forces. In obedience to these they would arrange themselves, and finally a.s.sume positions of rest, forming a coherent ma.s.s. Let us suppose the breeze, which now causes them to quiver, to disturb the a.s.sumed equilibrium. As often as disturbed there would be a constant effort on the part of the leaves to re-establish it; and in making this effort the ma.s.s of leaves would pa.s.s through different shapes and forms. If other leaves, moreover, were at hand endowed with similar forces, the attraction would extend to them--a growth of the ma.s.s of leaves being the consequence.

We have strong reason for a.s.suming that the ultimate particles of matter--the atoms and molecules of which it is made up--are endowed with forces coa.r.s.ely typified by those here ascribed to the leaves.

The phenomena of crystallisation load, of necessity, to this conception of molecular polarity. Under the operation of such forces the molecules of a seed, like our fallen leaves in the first instance, take up positions from which they would never move if undisturbed by an external impulse. But solar light and heat, which come to us as waves through s.p.a.ce, are the great agents of molecular disturbance. On the inert molecules of seed and soil these waves impinge, disturbing the atomic equilibrium, which there is an immediate effort to restore.

The effort, incessantly defeated--for the waves continue to pour in--is incessantly renewed; in the molecular struggle matter is gathered from the soil and from the atmosphere, and built, in obedience to the forces which guide the molecules, into the special form of the tree. In a general way, therefore, the life of the tree might be defined as an unceasing effort to restore a disturbed equilibrium. In the building of crystals Nature makes her first structural effort; we have here the earliest groping of the so-called 'vital force,' and the manifestations of this force in plants and animals, though, as already stated, indefinitely more complex, are to be regarded of the same mechanical quality as those concerned in the building of the crystal.

Consider the cycle of operations by which the seed produces the plant, the plant the flower, the flower again the seed, the causal line, returning with the fidelity of a planetary orbit to its original point of departure. Who or what planned this molecular rhythm? We do not know--science fails even to inform us whether it was ever 'planned' at all. Yonder b.u.t.terfly has a spot of orange on its wing; and if we look at a drawing made a century ago, of one of the ancestors of that b.u.t.terfly, we probably find the selfsame spot upon the wing. For a century the molecules have described their cycles. b.u.t.terflies have been begotten, have been born, and have died; still we find the molecular architecture unchanged. Who or what determined this persistency of recurrence? We do not know; but we stand within our intellectual range when we say that there is probably nothing in that wing which may not yet find its Newton to prove that the principles involved in its construction are qualitatively the same as those brought into play in the formation of the solar system. We may even take a step further, and affirm that the brain of man--the organ of his reason--without which he can neither think nor feel, is also an a.s.semblage of molecules, acting and reacting according to law. Here, however, the methods pursued in mechanical science come to an end; and if asked to deduce from the physical interaction of the brain molecules the least of the phenomena of sensation or thought, I acknowledge my helplessness. The a.s.sociation of both with the matter of the brain may be as certain as the a.s.sociation of light with the rising of the sun. But whereas in the latter case we have unbroken mechanical connection between the sun and our organs, in the former case logical continuity disappears. Between molecular mechanics and consciousness is interposed a fissure over which the ladder of physical reasoning is incompetent to carry us. We must, therefore, accept the observed a.s.sociation as an empirical fact, without being able to bring it under the yoke of _a priori_ deduction.

Such were the ponderings which ran habitually through my mind in the days of my scientific youth. They ill.u.s.trate two things--a determination to push physical considerations to their utmost legitimate limit; and an acknowledgment that physical considerations do not lead to the final explanation of all that we feel and know.

This acknowledgment, be it said in pa.s.sing, was by no means made with the view of providing room for the play of considerations other than physical. The same intellectual duality, if I may use the phrase, manifests itself in the following extract from an article ent.i.tled 'Physics and Metaphysics,' published in the 'Sat.u.r.day Review' for August 4, 1860:

'The philosophy of the future will a.s.suredly take more account than that of the past of the dependence of thought and feeling on physical processes; and it may be that the qualities of the mind will be studied through organic combinations as we now study the character of a force through the affections of ordinary matter. We believe that every thought and every feeling has its definite mechanical correlative--that it is accompanied by a certain breaking up and remarshalling of the atoms of the brain. This latter process is purely physical; and were the faculties we now possess sufficiently expanded, without the creation of any new faculty, it would doubtless be within the range of our augmented powers to infer from the molecular state of the brain the character of the thought acting on it, and, conversely, to infer from the thought the exact molecular condition of the brain. We do not say--and this, as will be seen, is all-important--that the inference here referred to would be an _a priori_ one. But by observing, with the faculties we a.s.sume, the state of the brain and the a.s.sociated mental affections, both might be so tabulated side by side that, if one were given, a mere reference to the table would declare the other. Our present powers, it is true, shrivel into nothingness when brought to bear on such a problem, but it is because of its complexity and our limits that this is the case.

The quality of the problem and of our powers are, we believe, so related, that a mere expansion of the latter would enable them to cope with the former. Why, then, in scientific speculation should we turn our eyes exclusively to the past? May it not be that a time is coming--ages no doubt distant, but still advancing--when the dwellers upon this fair earth, starting from the gross human brain of to-day as a rudiment, may be able to apply to these mighty questions faculties of commensurate extent? Given the requisite expansibility to the present senses and intelligence of man--given also the time necessary for their expansion--and this high goal may be attained. Development is all that is required, and not a change of quality. There need be no absolute breach of continuity between us and our loftier brothers yet to come.

We have guarded ourselves against saying that the inferring of thought from material combinations and arrangements would be an inference _a priori_. The inference meant would be the same in kind as that which the observation of the effects of food and drink upon the mind would enable us to make, differing only from the latter in the degree of a.n.a.lytical insight which we suppose attained. Given the ma.s.ses and distances of the planets, we can infer the perturbations consequent on their mutual attractions. Given the nature of a disturbance in water, air, or aether--knowing the physical qualities of the medium we can infer how its particles will be affected. In all this we deal with physical laws. The mind runs with certainty along the line of thought which connects the phenomena, and from beginning to end there is no break in the chain. But when we endeavour to pa.s.s by a similar process from the phenomena of physics to those of thought, we meet a problem which transcends any conceivable expansion of the powers which we now possess. We may think over the subject again and again, but it eludes all intellectual presentation. We stand at length face to face with the Incomprehensible. The territory of physics is wide, but it has its limits from which we look with vacant gaze into the region beyond. Let us follow matter to its utmost bounds, let us claim it in all its forms--even in the muscles, blood, and brain of man himself--as ours to experiment with and to speculate upon. Casting the term "vital force" from our vocabulary, let us reduce, if we can, the visible phenomena of life to mechanical attractions and repulsions. Having thus exhausted physics, and reached its very rim, a mighty Mystery still looms beyond us. We have, in fact, made no step towards its solution. And thus it will ever loom, compelling the philosophies of successive ages to confess that

"We are such stuff As dreams are made of, and our little life Is rounded by a sleep."

In my work on 'Heat,' published in 1863 and republished many times since, I employ the precise language thus extracted from the 'Sat.u.r.day Review.'

The distinction is here clearly brought out which I had resolved at all hazards to draw--that, namely, between what men knew or might know, and what they could never hope to know. Impart simple magnifying power to our present vision, and the atomic motions of the brain itself might be brought into view. Compare these motions with the corresponding states of consciousness, and an empirical nexus might be established; but 'we try to soar in a vacuum when we endeavour to pa.s.s by logical deduction from the one to the other.'

Among these brain-effects a new product appears which defies mechanical treatment. We cannot deduce motion from consciousness or consciousness from motion as we deduce one motion from another.

Nevertheless observation is open to us, and by it relations may be established which are at least as valid as those of the deductive reason. The difficulty may really lie in the attempt to convert a datum into an inference--an ultimate fact into a product of logic. My desire for the moment, however, is not to theorise, but to let facts speak in reply to accusation.

The most 'materialistic' speculation for which I was responsible, prior to the 'Belfast Address,' is embodied in the following extract from a brief article written as far back as 1865: 'Supposing the molecules of the human body, instead of replacing others, and thus renewing a pre-existing form, to be gathered first-hand from nature, and placed in the exact relative positions which they occupy in the body. Supposing them to have the same forces and distribution of forces, the same motions and distribution of motions--would this organised concourse of molecules stand before us as a sentient, thinking being? There seems no valid reason to a.s.sume that it would not. Or supposing a planet carved from the sun, set spinning round an axis, and sent revolving round the sun at a distance equal to that of our earth, would one consequence of the refrigeration of the ma.s.s be the development of organic forms? I lean to the affirmative.' This is plain speaking, but it is without 'dogmatism.' An opinion is expressed, a belief, a leaning--not an established 'doctrine.'

The burthen of my writings in this connection is as much a recognition of the weakness of science as an a.s.sertion of its strength. In 1867, I told the working men of Dundee that while making the largest demand for freedom of investigation; while considering science to be alike powerful as an instrument of intellectual culture, and as a ministrant to the material wants of men; if asked whether science has solved, or is likely in our day to solve, 'the problem of the universe,' I must shake my head in doubt. I compare the mind of man to a musical instrument with a certain range of notes, beyond which in both directions exists infinite silence. The phenomena of matter and force come within our intellectual range; but behind, and above, and around us the real mystery of the universe lies unsolved, and, as far as we are concerned, is incapable of solution.

While refreshing my mind on these old themes I appear to myself as a person possessing one idea, which so over-masters him that he is never weary of repeating it. That idea is the polar conception of the grandeur and the littleness of man--the vastness of his range in some respects and directions, and his powerlessness to take a single step in others. In 1868, before the Mathematical and Physical Section of the British a.s.sociation, then a.s.sembled at Norwich, I repeat the same well-worn note:

'In thus affirming the growth of the human body to be mechanical, and thought as exercised by us to have its correlative in the physics of the brain, the position of the "materialist," as far as that position is tenable, is stated. I think the materialist will be able finally to maintain this position against all attacks, but I do not think he can pa.s.s beyond it. The problem of the connection of body and soul is as insoluble in its modern form as it was in the pre-scientific ages.

Phosphorus is a const.i.tuent of the human brain, and a trenchant German writer has exclaimed, "Ohne Phosphor kein Gedanke!" That may or may not be the case; but, even if we knew it to be the case, the knowledge would not lighten our darkness. On both sides of the zone here a.s.signed to the materialist, he is equally helpless. If you ask him whence is this "matter" of which we have been discoursing--who or what divided it into molecules, and impressed upon them this necessity of running into organic forms--he has no answer. Science is also mute in regard to such questions. But if the materialist is confounded and science is rendered dumb, who else is prepared with an answer? Let us lower our heads and acknowledge our ignorance, priest and philosopher, one and all.'

The roll of echoes which succeeded the Lecture delivered by Professor Virchow at Munich on September 22, 1877, was long and loud. The 'Times' published a nearly full translation of the lecture, and it was eagerly commented on in other journals. Glances from it to an Address delivered by me before the Midland Inst.i.tute in the autumn of 1877, and published in this volume, were very frequent. Professor Virchow was held up to me in some quarters as a model of philosophic caution, who by his reasonableness reproved my rashness, and by his depth reproved my shallowness. With true theologic courtesy I was sedulously emptied, not only of the 'principles of scientific thought,' but of 'common modesty' and 'common sense.' And though I am indebted to Professor Clifford for recalling in the 'Nineteenth Century' for April the public mind in this connection from heated fancy to sober fact, I do not think a brief additional examination of Virchow's views, and of my relation to them, will be out of place here.

The key-note of his position is struck in the preface to the excellent English translation of his lecture--a preface written expressly by himself. 'Nothing,' he says, 'was farther from his intention than any wish to disparage the great services rendered by Mr. Darwin to the advancement of biological science, of which no one has expressed more admiration than himself. On the other hand, it seemed high time to him to enter an energetic protest against the attempts that are made to proclaim the problems of research as actual facts, and the opinions of scientists as established science.' On the ground, among others, that it promotes the pernicious delusions of the Socialist, Virchow considers the theory of evolution dangerous; but his fidelity to truth is so great that he would brave the danger and teach the theory, if it were only proved. 'However dangerous the state of things might be, let the confederates be as mischievous as they might, still I do not hesitate to say that from the moment when we had become convinced that the evolution theory was a perfectly established doctrine--so certain that we could pledge our oath to it, so sure that we could say, "Thus it is"--from that moment we could not dare to feel any scruple about introducing it into our actual life, so as not only to communicate it to every educated man, but to impart it to every child, to make it the foundation of our whole ideas of the world, of society, and the State, and to base upon it our whole system of education. This I hold to be a necessity.'

It would be interesting to know the persons designated by the p.r.o.noun 'we' in the first sentence of the foregoing quotation. No doubt Professor Haeckel would accept this canon in all its fulness, and found on it his justification. He would say without hesitation: 'I am convinced that the theory of evolution is a perfectly established doctrine, and hence on your own showing I am justified in urging its introduction into our schools.' It is plain, however, that Professor Virchow would not accept this retort as valid. His 'we' must cover something more than Professor Haeckel. It would probably cover more even than the audience he addressed; for he would hardly affirm, even if every one of his hearers accepted the theory of evolution, that that would be a sufficient warrant for forcing it upon the public at large. His 'we,' I submit, needs definition. If he means that the theory of evolution ought to be introduced into our schools, not when experts are agreed as to its truth, but when the community is prepared for its introduction, then, I think, he is right, and that, as a matter of social policy, Dr. Haeckel would be wrong in seeking to antedate the period of its introduction. In dealing with the community great changes must have timeliness as well as truth upon their side. But if the mouths of thinkers be stopped, the necessary social preparation will be impossible; an unwholesome divorce will be established between the expert and the public, and the slow and natural process of leavening the social lump by discovery and discussion will be displaced by something far less safe and salutary.

The burthen, however, of this celebrated lecture is a warning that a marked distinction ought to be made between that which is experimentally proved and that which is still in the region of speculation. As to the latter, Virchow by no means imposes silence.