Darwin

by Gamaliel Bradford

For the wonder and the interest of Darwin is, that, with such an eager and perpetual bent toward theorizing, he could keep the bent so fully under control. As Karl Pearson puts it, generally: ‘Hundreds of men have allowed their imagination to solve the universe, but the men who have contributed to our real understanding of natural phenomena have been those who were unstinted in their application of criticism to the product of their imaginations.’[450] Surely no man applied such criticism more carefully, more conscientiously, more constantly than Darwin. He analyzes his own position and sees the dangers of it: ‘Living so solitary as I do, one gets to think in a silly manner of one’s own work.’[451] He sees constantly how theory interferes and warps the judgment: ‘I have not a doubt that before many months are over I shall be longing for the most dishonest species as being more honest than the honestest theories.’[452] The possibility of error haunts him, torments him, and he knows well how apt his own speculative disposition is to mislead: ‘What you hint at generally is very, very true: that my work will be grievously hypothetical, and large parts by no means worthy of being called induction, my commonest error being probably induction from too few facts.’[453] As a consequence he was ever on his guard against being led astray. The tempting little demon of hypothesis might be luring round the corner: ‘It is as difficult not to form some opinion as it is to form a correct judgment.’[454] But whatever opinion was formed must be corrected, must be adjusted, must be tested, by the cold and rigid measure of fact. As he says himself, ‘I have steadily endeavored to keep my mind free so as to give up any hypothesis, however much beloved (and I cannot resist forming one on every subject), as soon as the facts are shown to be opposed to it.’[455] And one who knew him well and had studied him carefully says the same thing with equal emphasis: ‘His long experience had given him a kind of instinctive insight into the method of attack of any biological problem, however unfamiliar to him, while he rigidly controlled the fertility of his mind in hypothetical explanations by the no less fertility of ingeniously devised experiment.’[456]

In regard to this matter of speculative freedom and the tendency to let imagination run wild, it is interesting to watch Darwin’s comments on the general methods of others. The excess of abstinence he indeed deplores, recognizing that a man’s extreme caution may prevent him from theorizing enough: ‘How many astronomers have labored their whole lives on observations, and have not drawn a single conclusion.’[457] But the danger on the other side is so great and so ruinous that it cannot be enough insisted on, and indeed at times it makes all generalization suspicious and almost a thing to be eschewed: ‘I look at a strong tendency to generalize as an entire evil.’[458] At any rate, the theorist must never forget the subjective element, that his preconceptions and prejudices are apt to warp his judgment and distort his vision, till the keenest of observers and the sanest of thinkers may go astray: ‘the firmest conviction of the truth of a doctrine by its author seems, alas, not to be the slightest guarantee of truth.’[459]

The profit and the lesson of all which must be constantly borne home to oneself: ‘When I think of the many cases of men who have studied one subject for years, and have persuaded themselves of the truth of the foolishest doctrines, I feel sometimes a little frightened, whether I may not be one of these monomaniacs.’[460]

To appreciate fully Darwin’s combination of mental activity and fertility with moderation and restraint, it is well to place him between two extreme types of thinkers. On the one hand, there is the born essential reasoner, and logician, Spinoza, for instance, or Hegel, or Darwin’s own contemporary, Spencer, the man who to a greater or less extent takes fact for his foundation, but who by nature and temperament delights to weave an elaborate web of logical theory, rigid and perfect in its appearance of systematic deduction, but too apt in the end to treat facts with indifference if not disrespect. I like especially in this regard to compare Darwin with Lucretius. The De Rerum Natura is one of the most striking, enthralling examples of what I should call passionate thinking. Theoretical problems take hold of Lucretius like the ecstasies of love. He tears and wrenches at the roots of thought, determined to make them yield to the delving vigor of his eager search. Now Darwin has a broad and constant curiosity, his interest may well be called enthusiasm, and he himself uses the term passion for it: ‘Hence it has come to be a passion with me to try to connect all such facts by some sort of hypothesis.’[461] Yet in no phase of his nature should I be inclined ever to employ the general word, ‘passion,’ and it seems to me that every page of Lucretius is stamped with a devouring ardor different from anything Darwin knew.

On the other hand, over against these furious reasoners, I should set Darwin’s close contemporary, Sainte-Beuve, who, as I said in the previous chapter was, in some aspects, as admirable a representative of the scientific spirit as Darwin himself. The endless curiosity, the unlimited observation of fact, as embodied in the human subject, have never been more richly exemplified than in the great French critic. But Sainte-Beuve was no reasoner in the larger sense. He did not even avoid reasoning from mistrust: he had no taste for it, and when he dealt with it, it was always charily and with extreme reserve. He delighted to study and portray individuals and to allow those individuals, as it were, to classify themselves and so to point the way to general results.

Between these two extremes Darwin stands, as one who used reasoning to the fullest extent for the interpretation of fact, yet at the same time always stuck closely and rigidly to the fact itself, and would not allow it to be for an instant distorted by the reasoning process.

II

The supreme means for keeping theory on a basis of fact is of course unfailing, persistent, ever-varied experiment. In the preceding chapter we have seen observation lead naturally to experiment; but experiment is observation guided, directed, and illuminated by theory. And assuredly no scientist ever had the love and the habit of experiment more firmly fixed than Darwin. The explanation of phenomena was all very well in its place, essential, absorbing, but he would have agreed absolutely with Aristotle as to the proper ordering of the process: ‘After this we shall pass on to the discussion of causes. For to do this when the investigation of the details is complete, is the proper and natural method, and that whereby the subject and the premises of our argument will afterwards be rendered plain.’[462] The fascination of experiment in itself was endless and almost sufficing: ‘The love of experiment was very strong in him,’ says his son, ‘and I can remember the way he would say, “I shan’t be easy till I have tried it,” as if an outside force were driving him.’[463] There was a sense of adventure about it, of discovery, and he loved to try things that seemed almost fantastic and absurd: ‘If you knew some of the experiments (if they may be so-called) which I am trying, you would have a good right to sneer, for they are so absurd even in my opinion that I dare not tell you.’[464] And more concisely and vividly: ‘I am like a gambler and love a wild experiment.’[465] The best comment on which is the excellent remark of Professor Castle: ‘Most advances in practical affairs are made by those who have the courage to attempt what others with good reason think unattainable. When such attempts have succeeded, the world simply revises its classification of things attainable and unattainable, and makes a fresh start.’[466]

The first thing in regard to experiment is conditions. There are of course rough and elementary experiments, involving only simple principles, which do not require minute care in detail. But in many cases the nicest and most delicate preparation and adjustment are indispensable to ensure reliable results. The extensive equipment of modern laboratories was not at Darwin’s command, and though he had considerable financial resources, he could not afford the unlimited outlay of commercial research. Thus, we read of one of Mr. Burbank’s trials: ‘Forty thousand blackberry and raspberry hybrids were produced and grown until the fruit matured. Then from the whole lot a single variety was chosen as the best.... All others were uprooted with their crop of ripening berries, heaped up into a pile twelve feet wide, fourteen feet high, and twenty-two feet long, and burned. Nothing remained of this expensive and lengthy experiment, except the one parent plant of the new variety.’[467] Darwin could hardly work on any such elaborate scale as this. Yet, as one turns over his vast record of experiment, one is astonished to see how thorough and painstaking was his effort to avoid accidents and to provide for disturbing contingencies. Take, for instance, as a minor but significant illustration, his account of the difficulty in carrying out the specific fertilization of certain plants: ‘In making eighteen different unions, sometimes on windy days, and pestered by bees and flies buzzing about, some few errors could hardly be avoided. One day I had to keep a third man by me all the time to prevent the bees visiting the uncovered plants, for in a few seconds’ time they might have done irreparable mischief. It was also extremely difficult to exclude minute Diptera from the net.’[468]

Another vital consideration as to experiment, is that it should be kept impersonal. In most cases, if one is to experiment fruitfully and satisfactorily, there should be some special object in view, some particular point to be rejected or confirmed. Unless you know just what you are looking for, you are apt not to see. Again and again in Darwin’s book on Orchids, as in many of the others, we read that he made investigations and got no results, simply because he did not have in mind theoretical possibilities. When he had reasoned out what ought to happen or might happen, he often found that it did. The danger of this method is obvious. When the experimenter is so desperately anxious to see something, unless he is most carefully trained and disciplined, he will see it. It is not to be supposed that Darwin always escaped this danger, but few men have been more prepared for it or more ready to allow for it than he. His confession of prejudice, his recognition of the importance of certain points in his general theory and of his unwillingness to have anything interfere with them are among his greatest charms: ‘I remember well the time when the thought of the eye made me cold all over.... The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.’[469]