In complying with the wish of the publishers of Professor Haeckel's reply to Professor Virchow, that I should furnish a prefatory note expressing my own opinion in respect of the subject-matter of the controversy, Gay's homely lines, prophetic of the fate of those "who in quarrels interpose," emerge from some brain-cupboard in which they have been hidden since my childish days. In fact, the hard-hitting with which both the attack and the defence abound, makes me think with a shudder upon the probable sufferings of the unhappy man whose intervention should lead two such gladiators to turn their weapons from one another upon him. In my youth, I once attempted to stop a street fight, and I have never forgotten the brief but impressive lesson on the value of the policy of non-intervention which I then received.

But there is, happily, no need for me to place myself in a position which, besides being fraught with danger, would savour of presumption: Careful study of both the attack and the reply leaves me without the inclination to become either a partisan or a peacemaker: not a partisan, for there is a great deal with which I fully agree said on both sides; not a peacemaker, because I think it is highly desirable that the important questions which underlie the discussion, apart from the more personal phases of the dispute, should be thoroughly discussed. And if it were possible to have controversy without bitterness in human affairs, I should be disposed, for the general good, to use to both of the eminent antagonists the famous phrase of a late President of the French Chamber—"Tape dessus."

No profound acquaintance with the history of science is needed to produce the conviction, that the advancement of natural knowledge has been effected by the successive or concurrent efforts of men, whose minds are characterised by tendencies so opposite that they are forced into conflict with one another. The one intellect is imaginative and synthetic; its chief aim is to arrive at a broad and coherent conception of the relations of phenomena; the other is positive, critical, analytic, and sets the highest value upon the exact determination and statement of the phenomena themselves.

If the man of the critical school takes the pithy aphorism "Melius autem est naturam secare quam abstrahere"[1] for his motto, the champion of free speculation may retort with another from the same hand, "Citius enim emergit veritas e falsitate quam e confusione;"[2] and each may adduce abundant historical proof that his method has contributed as much to the progress of knowledge as that of his rival. Every science has been largely indebted to bold, nay, even to wild hypotheses, for the power of ordering and grasping the endless details of natural fact which they confer; for the moral stimulus which arises out of the desire to confirm or to confute them; and last, but not least, for the suggestion of paths of fruitful inquiry, which, without them, would never have been followed. From the days of Columbus and Kepler to those of Oken, Lamarck, and Boucher de Perthes, Saul, who, seeking his father's asses, found a kingdom, is the prototype of many a renowned discoverer who has lighted upon verities while following illusions, which, had they deluded lesser men, might possibly have been considered more or less asinine.

On the other hand, there is no branch of science which does not owe at least an equal obligation to those cool heads, which are not to be seduced into the acceptance of symmetrical formulÆ and bold generalisations for solid truths because of their brilliancy and grandeur; to the men who cannot overlook those small exceptions and insignificant residual phenomena which, when tracked to their causes, are so often the death of brilliant hypotheses; to the men, finally, who, by demonstrating the limits to human knowledge which are set by the very conditions of thought, have warned mankind against fruitless efforts to overstep those limits.

Neither of the eminent men of science, whose opinions are at present under consideration, can be said to be a one-sided representative either of the synthetic or of the analytic school. Haeckel, no less than Virchow, is distinguished by the number, variety, and laborious accuracy of his contributions to positive knowledge; while Virchow, no less than Haeckel, has dealt in wide generalisations, and, until the obscurantists thought they could turn his recent utterances to account, no one was better abused by them as a typical free-thinker and materialist. But, as happened to the two women grinding at the same mill, one has been taken and the other left. Since the publication of his famous oration, Virchow has been received into the bosom of orthodoxy and respectability, while Haeckel remains an outcast!

To those who pay attention to the actual facts of the case, this is a very surprising event; and I confess that nothing has ever perplexed me more than the reception which Professor Virchow's oration has met with, in his own and in this country; for it owes that reception, not to the undoubted literary and scientific merits which it possesses, but to an imputed righteousness for which, so far as I can discern, it offers no foundation. It is supposed to be a recantation; I can find no word in it which, if strictly construed, is inconsistent with the most extreme of those opinions which are commonly attributed to its author. It is supposed to be a deadly blow to the doctrine of evolution; but, though I certainly hold by that doctrine with some tenacity, I am able, ex animo, to subscribe to every important general proposition which its author lays down.

In commencing his address, Virchow adverts to the complete freedom of investigation and publication in regard to scientific questions which obtains in Germany; he points out the obligation which lies upon men of science, even if for no better reason than the maintenance of this state of things, to exhibit a due sense of the responsibility which attaches to their speaking and writing, and he dwells on the necessity of drawing a clear line of demarcation between those propositions which they have a fair right to regard as established truths, and those which they know to be only more or less well-founded speculations. Is any one prepared to deny that this is the first great commandment of the ethics of teaching? Would any responsible scientific teacher like to admit that he had not done his best to separate facts from hypotheses in the minds of his hearers; and that he had not made it his chief business to enable those whom he instructs to judge the latter by their knowledge of the former?

More particularly does this obligation weigh upon those who address the general public. It is indubitable, as Professor Virchow observes, that "he who speaks to, or writes for, the public is doubly bound to test the objective truth of that which he says." There is a sect of scientific pharisees who thank God that they are not as those publicans who address the public. If this sect includes anybody who has attempted the business without failing in it, I suspect that he must have given up keeping a conscience. For assuredly if a man of science, addressing the public, bethinks him, as he ought to do, that the obligation to be accurate—to say no more than he has warranty for, without clearly marking off so much as is hypothetical—is far heavier than if he were dealing with experts, he will find his task a very admirable mental exercise. For my own part, I am inclined to doubt whether there is any method of self-discipline better calculated to clear up one's own ideas about a difficult subject, than that which arises out of the effort to put them forth, with fulness and precision, in language which all the world can understand. Sheridan is said to have replied to some one who remarked on the easy flow of his style, "Easy reading, sir, is—hard writing;" and any one who is above the level of a scientific charlatan will know that easy speaking is "——hard thinking."

Again, when Professor Virchow enlarges on the extreme incompleteness of every man's knowledge beyond those provinces which he has made his own (and he might well have added within these also), and when he dilates on the inexpediency, in the interests of science, of putting forth as ascertained truths propositions which the progress of knowledge soon upsets—who will be disposed to gainsay him? Nor have I, for one, anything but cordial assent to give to his declaration, that the modern development of science is essentially due to the constant encroachment of experiment and observation on the domain of hypothetical dogma; and that the most difficult, as well as the most important, object of every honest worker is "sich ent-subjectiviren"—to get rid of his preconceived notions, and to keep his hypotheses well in hand, as the good servants and bad masters that they are.

I do not think I have omitted any one of Professor Virchow's main theses in this brief enumeration. I do not find that they are disputed by Haeckel, and I should be profoundly astonished if they were. What, then, is all the coil about, if we leave aside various irritating sarcasms, which need not concern peaceable Englishmen? Certainly about nothing that touches the present main issues of scientific thought. The "plastidule-soul" and the potentialities of carbon may be sound scientific conceptions, or they may be the reverse, but they are no necessary part of the doctrine of evolution, and I leave their defence to Professor Haeckel.

On the question of equivocal generation, I have been compelled, more conspicuously and frequently than I could wish, during the last ten years, to enunciate exactly the same views as those put forward by Professor Virchow; so that, to my mind, at any rate, the denial that any such process has as yet been proved to take place in the existing state of nature, as little affects the general doctrine.[3]

With respect to another side issue, raised by Professor Virchow, he appears to me to be entirely in the wrong. He is careful to say that he has no unwillingness to accept the descent of man from some lower form of vertebrate life; but, reminding us of the special attention which, of late years, he has given to anthropology, he affirms that such evidence as exists is not only insufficient to support that hypothesis, but is contrary to it. "Every positive progress which we have made in the region of prehistoric anthropology has removed us further from the demonstration of this relation."

Well, I also have studied anthropological questions in my time; and I feel bound to remark, that this assertion of Professor Virchow's appears to me to be a typical example of the kind of incautious over-statement which he so justly reprehends.

For, unless I greatly err, all the real knowledge which we possess of the fossil remains of man goes no farther back than the Quaternary epoch; and the most that can be asserted on Professor Virchow's side respecting these remains is, that none of them present us with more marked pithecoid characters than such as are to be found among the existing races of mankind.[4] But, if this be so, then the only just conclusion to be drawn from the evidence as it stands is, that the men of the Quaternary epoch may have proceeded from a lower type of humanity, though their remains hitherto discovered show no definite approach towards that type. The evidence is not inconsistent with the doctrine of evolution, though it does not help it. If Professor Virchow had paid as much attention to comparative anatomy and palÆontology as he has to anthropology, he would, I doubt not, be aware that the equine quadrupeds of the Quaternary period do not differ from existing EquidÆ in any more important respect than these last differ from one another; and he would know that it is, nevertheless, a well-established fact that, in the course of the Tertiary period, the equine quadrupeds have undergone a series of changes exactly such as the doctrine of evolution requires. Hence sound analogical reasoning justifies the expectation that, when we obtain the remains of Pliocene, Miocene, and Eocene AnthropidÆ, they will present us with the like series of gradations, notwithstanding the fact, if it be a fact, that the Quaternary men, like the Quaternary horses, differ in no essential respect from those which now live.

I believe that the state of our knowledge on this question is still justly summed up in words written some seventeen years ago:—

"In conclusion, I may say, that the fossil remains of man hitherto discovered do not seem to me to take us appreciably nearer to that lower pithecoid form by the modification of which he has probably become what he is. And considering what is now known of the most ancient races of men; seeing that they fashioned flint axes, and flint knives, and bone skewers of much the same pattern as those fabricated by the lowest savages at the present day, and that we have every reason to believe the habits and modes of living of such people to have remained the same from the time of the mammoth and the tichorhine rhinoceros till now, I do not know that the result is other than might be expected."[5]

I have seen no reason to change the opinion here expressed, and so far from the fact being in the slightest degree opposed to a belief in the evolution of man, all that has been learned of late years respecting the relation of the Recent and Quaternary to the Tertiary mammalia appears to me to be in striking harmony with what we know respecting Quaternary man, supposing man to have followed the general law of evolution.

The only other collateral question of importance raised by Professor Virchow is, whether the doctrine of evolution should be generally taught in schools or not. Now I cannot find that Professor Virchow anywhere distinctly repudiates the doctrine; all that he distinctly says is that it is not proven, and that things which are not proven should not be authoritatively instilled into the minds of young people.

If Professor Virchow will agree to make this excellent rule absolute, and applicable to all subjects that are taught in schools, I should be disposed heartily to concur with him.

But what will his orthodox allies say to this? If "not provenness" is susceptible of the comparative degree, by what factor must we multiply the imperfection of the evidence for evolution in order to express that of the evidence for special creation; or to what fraction must the value of the evidence in favour of the uninterrupted succession of life be reduced in order to express that in support of the deluge? Nay, surely even Professor Virchow's "dearest foes," the "plastidule soul" and "Carbon & Co.," have more to say for themselves, than the linguistic accomplishments of Balaam's ass and the obedience of the sun and moon to the commander of a horde of bloodthirsty Hebrews! But the high principles of which Professor Virchow is so admirable an exponent do not admit of the application of two weights and two measures in education; and it is surely to be regretted that a man of science of great eminence should advocate the stern bridling of that teaching which, at any rate, never outrages common sense, nor refuses to submit to criticism, while he has no whisper of remonstrance to offer to the authoritative propagation of the preposterous fables by which the minds of children are dazed and their sense of truth and falsehood perverted. Professor Virchow solemnly warns us against the danger of attempting to displace the Church by the religion of evolution. What this last confession of faith may be I do not know, but it must be bad indeed if it inculcates more falsities than are at present foisted upon the young in the name of the Church.

I make these remarks simply in the interests of fair play. Far be it from me to suggest that it is desirable that the inculcation of the doctrine of evolution should be made a prominent feature of general education. I agree with Professor Virchow so far, but for very different reasons. It is not that I think the evidence of that doctrine insufficient, but that I doubt whether it is the business of a teacher to plunge the young mind into difficult problems concerning the origin of the existing condition of things. I am disposed to think that the brief period of school-life would be better spent in obtaining an acquaintance with nature, as it is; in fact, in laying a firm foundation for the further knowledge Which is needed for the critical examination of the dogmas, whether scientific or anti-scientific, which are presented to the adult mind. At present, education proceeds in the reverse way; the teacher makes the most confident assertions on precisely those subjects of which he knows least; while the habit of weighing evidence is discouraged, and the means of forming a sound judgment are carefully withheld from the pupil.

Professor Virchow is known to me only as he is known to the world in general—by his high and well-earned scientific reputation. With Professor Haeckel, on the other hand, I have the good fortune to be on terms of personal friendship. But in making the preceding observations, I should be sorry to have it supposed that I am holding a brief for my friend, or that I am disposed to adopt all the opinions which he has expressed in his reply. Nevertheless, I do desire to express my hearty sympathy with his vigorous defence of the freedom of learning and teaching; and I think I shall have all fair-minded men with me when I also give vent to my reprobation of the introduction of the sinister arts of unscrupulous political warfare into scientific controversy, manifested in the attempt to connect the doctrines he advocates with those of a political party which is, at present, the object of hatred and persecution in his native land. The one blot, so far as I know, on the fair fame of Edmund Burke is his attempt to involve Price and Priestley in the furious hatred of the English masses against the authors and favourers of the revolution of 1789. Burke, however, was too great a man to be absurd, even in his errors; and it is not upon record that he asked uninformed persons to consider what might be the effect of such an innovation as the discovery of oxygen on the minds of members of the Jacobin Club.

Professor Virchow is a politician—maybe a German Burke, for anything that I know to the contrary; at any rate, he knows the political value of words; and, as a man of science, he is devoid of the excuses that might be made for Burke. Nevertheless, he gravely charges his hearers to "imagine what shape the theory of descent takes in the head of a Socialist."

I have tried to comply with this request, but I have utterly failed to call up the dread image; I suppose because I do not sufficiently sympathise with Socialists. All the greater is my regret that Professor Virchow did not himself unfold the links of the hidden bonds which unite evolution with revolution, and bind together the community of descent with the community of goods.

Professor Virchow is, I doubt not, an accomplished English scholar. Let me commend the "Rejected Addresses" to his attention. For since the brothers Smith sang—

"Who makes the quartern loaf and Luddites rise,"—
Who fills the butchers' shops with large blue flies,

there has been nothing in literature at all comparable to the attempt to frighten sober people by the suggestion that evolutionary speculations generate revolutionary schemes in Socialist brains. But then the authors of the "Rejected Addresses" were joking, while Professor Virchow is in grim earnest; and that makes a great difference in the moral aspect of the two achievements.