Whether the particular shape which the doctrine of Evolution, as applied to the organic world, took in Darwin's hands would prove to be final or not, was to me a matter of indifference. In my earliest criticisms of the Origin I ventured to point out that its logical foundation was insecure so long as experiments in selective breeding had not produced varieties which were more or less infertile; and that insecurity remains up to the present time. But, with any and every critical doubt which my sceptical ingenuity could suggest, the Darwinian hypothesis remained incomparably more probable than the creation hypothesis. And if we had none of us been able to discern the paramount significance of some of the most patent and notorious of natural facts, until they were, so to speak, thrust under our noses, what force remained in the dilemma—creation or nothing? It was obvious that hereafter the probability would be immensely greater, that the links of natural causation were hidden from our purblind eyes, than that natural causation should be incompetent to produce all the phenomena of nature. The only rational course for those who had no other object than the attainment of truth was to accept "Darwinism" as a working hypothesis and see what could be made of it. Either it would prove its capacity to elucidate the facts of organic life or it would break down under the strain. This was surely the dictate of common sense, and for once common sense carried the day.
Mention has been made of the instant support he was able to lend the Origin in the Times review of the book, and the extension of its doctrines in regard to man. Even before the book appeared, however, he began to act as what Darwin laughingly called his "general agent." His address on "Persistent Types" (June, 1859) aimed at clearing up in advance one of the obvious objections raised against acceptance of the doctrine of Evolution—namely, how is it that, if evolution is ever progressive, progress is not universal? How is it that all forms do not necessarily advance, and that simple organisms still exist? As it happened, Darwin did not discuss this point when he first put the Origin together, and speedily came to regard this as the most serious omission in the book.
Great, then, was the debt of all science to Darwin. And not of science only. The fight for freedom of thought and speech in science, into which Huxley especially threw himself, was the more successful because the immediate cause he upheld was so overwhelmingly strong in reason and demonstration; and, the supreme curb upon thought being once broken, a wider freedom was gained.
For Darwin, therefore, Huxley had the reverence due to one who had forged a new and mighty weapon in the war for plain truth. But, while he could not but uphold a theory so much in accord with his own knowledge and so fruitful in its promise of new knowledge, whether the author of it were his friend or not, admiration and affection for a man of such utter sincerity, such selfless respect for truth, and warm personality, led him, when those views were stupidly or maliciously attacked, to take more trouble in his defence and support, and to strike out much harder at his adversary than he would otherwise have done. Darwin's friends were well assured that the scanty time which his health allowed for work was far too precious to be wasted in controversy; for his own sake and for the sake of the calm atmosphere in which a great theory should be worked out, they thought that the battling on a lower plane should be left to them. "You ought to be like one of the blessed gods of Elysium, and let the inferior deities do battle with the infernal powers." "If I say a savage thing," Huxley told him, "it is only 'pretty Fanny's way'; but if you do, it is not likely to be forgotten." Hence a dash of personal pleasure was infused into the duty of upholding and defending the bringer of new light.
The acquaintance had begun about 1851; there was a common bond in their sea experiences and explorations, as well as in their search after a wider philosophy, to include the teachings of natural science; the older man found in the younger a source of much biological and other information, a suggestive critic and a stimulating companion. Their relations took a long step towards intimacy after 1861, when, after the loss of her eldest child, Mrs. Huxley and her other children made a long stay at Down, and entered upon a life-long friendship with Mrs. Darwin and the family. Thereafter followed many visits to Down, and, whenever Darwin was in London, the certainty of half-an-hour's keen talk—all that the doctor allowed—with his friend and fellow-worker on some critical question of the moment.
Darwin's admiration of his friend's powers was outspoken. To quote one or two expressions of it: Huxley had delivered, in 1862, six lectures to working men, which were printed off each week as delivered in "little green pamphlets," under the general title of "On Our Knowledge of the Causes of the Phenomena of Organic Nature," winding up with an account of the bearing of the Origin upon the complete theory of these causes. Acknowledging Nos. IV and V, Darwin writes:—
They are simply perfect. They ought to be largely advertised; but it is very good in me to say so, for I threw down No. IV with this reflection: "What is the good of me writing a thundering big book when everything is in this green little book, so despicable for its size?" In the name of all that is good and bad, I may as well shut up shop altogether.
After reading the article "Mr. Darwin's Critics" in 1871, he wrote yet more enthusiastically. Mr. Mivart, in an apologia for the attitude of Roman Catholicism towards Evolution, twitted the generality of men of science with their ignorance of the real doctrines of his Church, and cited the Jesuit theologian, Suarez, the latest great representative of scholasticism, as following St. Augustine in asserting derivative creation—that is, evolution from primordial matter endowed with certain powers. Huxley thereupon examined the works of the learned Jesuit, and found not only that the particular reference was not to the point, but that, in his tract on the "Six Days of Creation," Suarez expressly rejects the doctrine and reprehends Augustine for holding it. "So," write Huxley gleefully at the irony of the situation, "I have come out in the new character of a defender of Catholic orthodoxy, and upset Mivart out of the mouth of his own prophet."
In the course of a most appreciative letter Darwin exclaimed:—
What a wonderful man you are to grapple with those old metaphysico-divinity books…. The pendulum is now swinging against our side, but I feel positive it will soon swing the other way; and no mortal man will do half as much as you in giving it a start in the right direction, as you did at the commencement.