Still another example of theorizing is the doctrine of pangenesis. Darwin’s general theory of evolution which dealt so much with heredity, was closely complicated with the difficulty of understanding how one minute reproductive cell could transmit by inheritance all the complicated variety of organs and functions in a highly developed plant or animal. To meet this difficulty he devised the explanation of pangenesis (he doubts about the name, because ‘my wife says it sounds wicked, like pantheism’),[367] that is, the idea that the primitive cell contains a great number of gemmules, each transmitting and originating some particular organ with its varied functions. Here again the theory, as Darwin conceived it, did not find general acceptance, though in some respects it surprisingly anticipates the results of the latest modern research. But the interesting thing is to see the ardor with which its inventor worked it out and the elaborate argument with which he carries it through the latter part of the great work on ‘Animals and Plants under Domestication.’ It is difficult, he admits. He does not blame any one for disputing it, or for rejecting it, or even for laughing at it. ‘The hypothesis of Pangenesis, as applied to the several great classes of facts just discussed, no doubt is extremely complex, but so are the facts.’[368] And then he lets his imagination range more widely than usual in contemplating possible deductions and consequences: ‘No other attempt, as far as I am aware, has been made, imperfect as this confessedly is, to connect under one point of view these several grand classes of facts. An organic being is a microcosm—a little universe, formed of a host of self-propagating organisms, inconceivably minute and numerous as the stars in heaven.’[369] Yet here again he introduces the inevitable reservation and in his Autobiographical Sketch he says: ‘Towards the end of the work I give my well-abused hypothesis of Pangenesis. An unverified hypothesis is of little or no value; but if any one should hereafter be led to make observations by which some such hypothesis could be established, I shall have done good service.’[370]
It seems sometimes surprising that, with this marked bent towards abstract speculation, which it was so difficult to control, Darwin should have been always so indifferent to philosophical thought on the ultimate questions of the universe. He admits that he knew little of metaphysics and cared little for them. But this again is instructive as to the peculiar balance of his temperament. He liked to speculate, but he would not speculate for a moment without a firm foundation of fact. His feet must be based first on the solid tangible earth. Then if his head would not reach the clouds, he would keep out of them.
IV
It will be profitable to consider more in detail some specific elements of Darwin’s reasoning. In the first place, we have seen everywhere and in all connections that his propensity to eager theorizing was tempered with an unfailing sense of doubt and mistrust. He was indeed always disposed to act in the spirit of Weisman’s remark: ‘When we are confronted with facts which we see no possibility of understanding save on a single hypothesis, even though it be an undemonstratable one, we are naturally led to accept the hypothesis, at least until a better one can be found.’[371] And he recognized fully the force of the comment which Huxley makes on a phrase of Goethe, to the effect that doubt must not be blighting or destructive, but fruitful and stimulating: ‘Goethe has an excellent aphorism defining that state of mind which he calls “Thätige Skepsis”—active doubt. It is doubt which so loves truth that it neither dares rest in doubting nor extinguish itself by unjustified belief.’[64] At the same time, the doubt was there, was temperamental, and could not be altogether extinguished, even when the rush of the logical impetus was fullest. One beautiful expression of it among many is, ‘When you say you cannot master the train of thoughts, I know well enough that they are too doubtful and obscure to be mastered. I have often experienced what you call the humiliating feeling of getting more and more involved in doubt the more one thinks of the facts and reasoning on doubtful points.’[65] The truth is, that Darwin had in a high degree the quality, often so hampering to the man of practical action, but invaluable to the thinker, of getting outside of himself and his own point of view and criticizing it as if it were the standpoint of some one else. He himself indicates this forcibly in connection with returning to one’s ideas after an interval: ‘The delay in this case, as with all my other books, has been a great advantage to me; for a man after a long interval can criticize his own work, almost as well as if it were that of another person.’[66] Some men can.
Another characteristic of Darwin’s mental processes is his way of meeting difficulties. The born reasoner is apt to slur over obstacles and objections, to devote himself with endless ingenuity to eliminating them rather than facing them squarely. Darwin was ingenious enough, but he did not dodge difficulties. Instead of doing so, his propensity was, if anything, to make them and seek them. It was said of Pasteur, so like Darwin in many points: ‘No adversary of M. Pasteur had formulated this argument; but M. Pasteur, who had within himself an ever-present adversary, always on the watch and determined to yield only to the force of accumulated evidence, himself raised the objection.’[67] So Darwin. As he himself records, and no thinker ever laid down a more significant principle or one more revealing for his own mental constitution: ‘I had, also, during many years followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favorable ones.’[68] And the intense consciousness of objections and difficulties appears even more vividly in the sentence: ‘I cannot too strongly express my conviction of the general truth of my doctrines, and God knows I have never shirked a difficulty.’[69]
The recognition of obstacles and complications constantly popping up from everywhere naturally necessitated endless revision and recasting. Here again, the habitual reasoner, having once set his mould is reluctant to alter it. Not so Darwin. There are indeed times when even he rebels and declares that it will be more fruitful to follow new paths than to be perpetually adjusting the old. But in general his readiness to alter and reconstruct is unlimited. He revises and works over his books. In doing so he showed his characteristic disposition to accept and defer to the judgment of others. How charming is his daughter’s account of this: ‘He was always so ready to be convinced that any suggested alteration was an improvement, and so full of gratitude for the trouble taken. I do not think that he ever used to forget to tell me what improvement he thought that I had made, and he used almost to excuse himself if he did not agree with any correction. I think I felt the singular modesty and graciousness of his nature through thus working for him in a way I never should otherwise have done.’[70] There is no better way to appreciate the extent and the persistence of Darwin’s revision than to make even a cursory comparison of the first and the last editions of the ‘Origin.’ Almost every page shows minor or considerable changes, and while some are no doubt mere matters of language, many have a bearing, however slight, on the trend of the reasoning, deepening, or strengthening, or clarifying it.
It is profitable also to watch Darwin’s attitude towards argument, the direct interchange of view by those who take different sides of a case and are at once eager to advance their own and to detect the flaws in their opponent’s. It is very evident that he was not a quick and natural arguer, as was Huxley, for instance. His son says: ‘He used to say of himself that he was not quick enough to hold an argument with any one, and I think this was true. Unless it was a subject on which he was just then at work, he could not get the train of argument into working order quickly enough.’[71] And Darwin confesses the same thing with his unfailing, charming naïveté, in a letter to Hooker: ‘I am astonished at your success and audacity. It is something unintelligible to me how any one can argue in public like orators do. I had no idea you had this power.’[72]
Arguments haunted him, agitated him, disturbed him. Active discussion was apt to be followed by a broken night, filled with the things that might and should have been said and were not. Even of a conversation quite remote from his scientific interest he says: ‘Your slave discussion disturbed me much; but as you would care no more for my opinion on this head than for the ashes of this letter, I will say nothing except that it gave me some sleepless, most uncomfortable hours.’[73]
The gift I have before suggested, of getting outside of your own position and judging it as another would, while it benefits the results of argument, is most hampering in the process, since one finds oneself stating one’s adversary’s case sometimes more forcibly than he does himself. Darwin often repeats the principle I have quoted earlier, of recognizing and recording objections, and he sums up his method in regard to his main theory: ‘I have for some time determined to give the arguments on both sides (as far as I could) instead of arguing on the mutability side alone.’[74]
Yet in spite of all the strain and effort of argument, he liked it and believed in it. In the concluding chapter of the ‘Origin’ he says: ‘This whole volume is one long argument.’[75] It certainly is. Elsewhere he says of a personal conversation: ‘I was particularly glad of our discussion after dinner; fighting a battle with you always clears my mind wonderfully.’[76] To get the mind clear, to illuminate and elucidate the complicated tangles of thought and theory, that was always the object, and if verbal battles helped it on, they were welcome.