The Philosophical Breakfast Club
Page 44
Whewell’s writings on scientific method, along with Herschel’s, served as a model for Darwin in constructing his argument for evolution by natural selection. He read Whewell’s History of Inductive Sciences at least twice—his diary indicates that he had gone through the book carefully for a second time in the fall of 1838. In a letter to Whewell the following spring, Darwin told him that “to see so clearly the steps by which all the great discoveries have been come to is a capital lesson to every one, even to the humblest follower of science and I hope I have profited by it.”48 Two years later, after reading Herschel’s review of the History and the Philosophy of the Inductive Sciences in the Quarterly Review, Darwin made a note to himself: “I must study Whewell on Philosophy of Science.”49
Darwin finally published his theory in 1859, spurred on by learning that another man, Alfred Russel Wallace, had come to a very similar theory as his—Wallace had realized both the importance of the struggle for existence and the introduction of new species it helps bring about. Darwin’s hand was forced, lest he lose his standing as the “discoverer” of the theory. He did not want to end up like John Couch Adams, forever living with the indignity of taking second place in the race to scientific truth. Darwin set to work and quickly wrote his revolutionary work, On the Origin of Species. His book can be seen as encoding Whewell and Herschel’s philosophy of science, especially what they had considered the strongest type of evidence for a scientific theory—what Whewell had dubbed consilience.
Both Herschel and Babbage had already discussed the power of this kind of evidence in their works: Herschel in the Preliminary Discourse, and Babbage in his Ninth Bridgewater Treatise.50 But Whewell gave the most detailed and interesting description of it in his Philosophy of the Inductive Sciences. “The Consilience of Inductions,” he explained, “takes place when an Induction, obtained from one class of facts, coincides with an Induction obtained from another different class.”51 Whewell’s favorite example of a consilient theory was Newton’s law of universal gravitation. In the Mathematical Principles of Natural Philosophy, where he announced his discovery, Newton described how his study of the moons of Jupiter showed him that they were retained in their orbits around Jupiter by a force directly proportional to the products of the masses of the moons and Jupiter, and inversely proportional to the squares of the distances of the centers of the moons from the center of the planet. His study of the earth’s moon led to the same conclusion, that our satellite was held in its orbit by a force directly proportional to the product of the masses of the moon and earth, and inversely proportional to the square of the distance between the center of the moon and the center of the earth. Similarly, Newton’s study of the planets led to the conclusion that the planets, too, were retained in their orbits around the sun by a force directly proportional to the product of the masses and inversely proportional to the square of the distances of the centers of the planets to the center of the sun. Newton found, as well, that falling bodies are governed by a force directly proportional to the product of the masses of the bodies and the earth, and inversely proportional to the square of the distances of the bodies from the center of the earth.
All these different kinds of phenomena “leapt to the same point,” as Whewell put it: they each led to the same inverse-square law of attraction, leading Newton to his universal law of gravitation, which generalized this inverse-square force of attraction even further: every object in the universe attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Newton then used this law to account for other phenomena, such as some facts about the motion of the tides. What Newton’s law did so brilliantly was to provide a causal unification of the forces of the universe, by bringing together phenomena previously thought of as distinct, showing that they all fall under the same law and have the same cause. Who before Newton thought that the motion of planets and satellites, falling objects, and the tides were all governed by the same force? Consilience shows us, Whewell argued, that the theory is very probably true, because it would be highly unlikely for a false theory to causally unify so many diverse phenomena.
Darwin saw that his theory would be the most strongly supported if he could show how it causally unified facts in many different fields, the way Newton’s law of universal gravitation did. He set out to fulfill this requirement, observing, experimenting, reading, and collecting data of all sorts. He began to breed pigeons obsessively, seeking observational evidence for the inheritance of characteristics such as black wing feathers or heads of diverse shapes. He studied barnacles, inquiring into every known species of that crustacean, finding tiny adaptations that made one variety more successful than another in surviving its watery environment. The study of barnacles revealed to Darwin the high rate of variation that occurred in nature. (He spent so many hours, for so many years, on barnacles, that his children grew up believing that all fathers studied barnacles. “Where does your father do his barnacles?” one of his sons asked a young friend.)52
When he finally published the Origin of Species, it was packed with evidence, showing how his theory of evolution by natural selection provided a causal explanation for many different kinds of facts: those in the realms of classification of organisms (how they are sorted into groups), biogeography (patterns of distribution of species), comparative anatomy (homologous structures), paleontology (especially the fossil record, which shows both the extinction of old species and the arrival of new ones), and other areas. For instance, his theory provided a causal explanation for the observed cases of homological structures, such as the wing of a bat and the arm of man, which share a similar arrangement of bones. According to Darwin’s theory, homologous structures descend from a common ancestor, and since the changes that eventually result in the branching off of different species happen gradually, the main pattern of composition remains the same.53 Similarly, the fitness of species to their environments could be causally explained by the theory; individuals not well suited to survive in an environment would tend to die before having the chance to reproduce, and so they would be “weeded out,” as it were, leaving only individuals that are well suited to the environment. The species Ursus maritimus (polar bear) has white fur not because God made it that way, but because any bears with black fur born in the snowy Arctic are hunted down by their predators and killed before reaching the age of reproduction; only white bears have the chance to survive and reproduce, creating more white bears.
When the Origin of Species was first published, it was a literary and scientific event. The first edition sold out on its very first day, November 24, 1859. Everyone, it seemed, was reading and talking about it. George Eliot told a friend, using the terminology from Whewell’s History of the Inductive Sciences, “We have been reading Darwin’s Book … just now: it makes an epoch.”54
At the same time, Darwin’s greatest fears were realized: many of the reviews lambasted the author for his faulty scientific method. Sedgwick and Owen, for example, took Darwin to task for having “departed from the true inductive track.”55 In later editions of the book, Darwin emphasized more strongly the consilience of the theory, how it explains such a wide variety of types of facts, arguing that “I cannot believe that a false theory would explain … the several large classes of facts above specified.”56
NOT SURPRISINGLY, GIVEN the view of God as a computer programmer that he had been endorsing for decades now, Babbage was an early convert to evolutionary theory. He had no difficulty accepting the idea that God set up His Creation so that species would evolve, naturally, without any further intervention on His part. In the opening pages of his Passages from the Life of a Philosopher, published in 1864, Babbage noted that Darwin’s view of our origin is “philosophic” (that is, scientific) but “unromantic.” Yet he claimed that the “continual accumulation of evidence” had convinced him that it was probably true.57
But Darwin was more concerned with what Herschel
and Whewell would think. The year before, he had seen the two elder statesmen of science at the British Association meeting in Leeds; Whewell, at sixty-four, now white-haired and said to be “grow[ing] squarer and more Bishop-like than ever,” had been the head of the Mathematical and Physical Sciences section; Herschel, increasingly frail at sixty-six, had presided over the Chemical section; and Darwin himself had been the chair of the Zoology and Botany section.58 He sent both men copies of the book as soon as it came off the printing press. In the letter accompanying Herschel’s copy, Darwin acknowledged his debt to the older man: “Scarcely anything in my life made so deep an impression on me” as the Preliminary Discourse. “It made me wish to try to add my mite to the accumulated store of natural knowledge.”59 Although he had, Darwin believed, followed their prescriptions for gathering and presenting the best kind of evidence for a scientific theory, neither Herschel nor Whewell enthusiastically accepted evolutionary theory. Herschel’s immediate response was the most cutting: he referred to evolution by natural selection as “the law of higgedly-piggedly” (that is, a random mess), which particularly pained Darwin when he heard of it. Later, in a note added to an 1861 reprinting of his Physical Geography—which had originally appeared in the Encyclopaedia Britannica in 1859—Herschel explained that he could not accept “the principle of arbitrary and casual variation and natural selection as sufficient account, per se, of the past and present organic world.” It would be, he said, just like asserting that a process of randomly combining words could result in the works of Shakespeare or Newton’s Principia. Rather, Herschel argued, “an intelligence, guided by a purpose, must be continually in action to bias the directions of the steps of change.” As in his earlier letter to Lyell, Herschel continued to assert that “we do not mean to deny that such intelligence may act according to law.”60
What upset Herschel about Darwin’s theory was the fact that, according to it, the variations that crop up from time to time are completely random. Today, with our knowledge of genetics—Gregor Mendel did not publish his famous paper on his pea-plant experiments until 1866, and his work was not widely known until 1900—we would call them “random mutations.” Darwin was arguing that there is no connection between what the individual needs to survive in his environment, and what variations arise. The faster wolf was not born faster because there was more competition for edible animals, making it useful to be able to get to the prey faster. Only a “random variation,” as Darwin called it, happened to give this wolf an edge over his slower brothers in getting enough to eat. It was just as likely that the wolf would have been born with an unhelpful variation, such as one shorter leg, in which case it would have been more likely to die before reproducing. Herschel ardently believed that there was some guiding force, some divine intelligence, that was in control of the variations, even if this control had been planned at the start of Creation and built into the laws governing the natural world. It could not be just by chance, Herschel argued, that variations useful to individual organisms arose. It was hard indeed for the prejudice against a chance-driven universe to loosen its grip on the scientists of the day. As Whewell had put it plaintively in his Bridgewater Treatise, “How unlike chance every thing looks!”61 Even strong supporters of Darwin, such as Asa Gray, hoped he would incorporate some kind of guiding force into his theory.62
In contrast to Herschel’s reaction, Whewell’s response pleasantly surprised Darwin—of course, he had had rather low expectations, knowing Whewell’s view of the fixity of species from reading the History of the Inductive Sciences. Whewell told Darwin, “Probably you will not be surprised to be told that I cannot, yet at least, become a convert to your doctrines. But there is so much of thought and fact in what you have written that it is not to be contradicted without a careful selection of the ground and manner of the dissent.”63 Darwin was so pleased that he sent Whewell’s letter to Lyell, showing him that Whewell at least “is not horrified with us.”64
Whewell never became a convert to evolution; on the contrary, he published a new preface for his Bridgewater Treatise in 1864 in which he referred to the recent claim that “the structure of animals has become what it is by the operation of external circumstances and internal appetencies” rather than by the special creation of God. He criticized this view for “assert[ing] the world to be the work of chance.” Rallying the old arsenal of pro-design arguments and examples, Whewell claimed that only an intelligent designer could account for the intricacy and perfect fitness of structures found in nature, such as the human eye.65 Like Herschel, Whewell was concerned about what he considered the gap in Darwin’s argument: random variations, he believed, could not have brought about something as wonderful as the human eye. Even Darwin still worried about this example. He told Asa Gray in 1860 that “the eye to this day gives me a cold shudder!”66
Yet Whewell was impressed with the amount and broad scope of Darwin’s evidence—he saw that Darwin had made some steps toward showing that his theory was consilient. This is why Whewell did not go out of his way to criticize Darwin publicly, as he had the author of the Vestiges of the Natural History of Creation. When that earlier work came out, Whewell published a book in which he compiled all the passages from his earlier writings arguing against transmutation of species. Darwin’s book, by contrast, did not trigger the same kind of reaction.
At the same time, however, Whewell did not believe that Darwin’s theory of evolution was strongly consilient, the way Newton’s law of universal gravitation was. In his 1838 presidential address to the Geological Society, Whewell had laid out the challenge for any purely naturalistic account of man’s origin. “Even if we had no Divine record to guide us,” Whewell argued, “it would be most unphilosophical [that is, unscientific] to attempt to trace back the history of man without taking into account the most remarkable facts in his nature.”67 It was impossible to account adequately for the origin of species, including the origin of man, Whewell believed, without explaining man’s origin as an intellectual and moral being. After all, it was not hard to imagine that our bodies, so like that of the orangutans recently exhibited around London, descended from the primates. But surely our minds—with our conscience, our sympathy for others, our reasoning skills, and our language—surely these were quite unlike anything else existing in nature, and required a Divine Creator? As Whewell had written in his Plurality of Worlds six years earlier, “The introduction of reason and intelligence upon the Earth is no part nor consequence of the series of animal forms. It is a fact of an entirely new kind.” Darwin’s theory of evolution could not be completely consilient until it could explain the most important distinctive fact about the species of mankind.
Darwin knew that Whewell was right about this. Even Charles Lyell and Asa Gray were by then complaining publicly that natural selection could not explain the distinctive features of humans, especially our moral nature. Darwin recognized that he needed to show that just as the physical nature of man could have originated in the physical nature of the higher primates, so too man’s reason and morality could have arisen from other animals. In his Descent of Man, published five years after Whewell’s death, Darwin addressed that issue. He explained that his objective in the book was “solely to shew that there is no fundamental difference between man and the higher mammals in their mental faculties.” In the process Darwin showed that each of the faculties thought to be unique to humans—moral reasoning, sympathy, aesthetic enjoyment—can be found as well, to a different degree, of course, in some animal species. As a reviewer of the book in the Annual Register put it, Darwin showed that animals shared the emotions of “terror, suspicion, courage, good humor, bad humor, revenge, affection”—something with which any dog lover would agree.68 Darwin hoped to provide evidence that man’s mental nature, no less than his physical nature, could evolve by natural causes.
But what is most remarkable, perhaps, is that neither Herschel nor Whewell strongly and publicly denounced Darwin, as did so many of their friends and acquaintances. A
s Darwin had expected, evolutionary theory was seen as opposing dearly held religious belief in the special creation of species by God. The issue was not biblical fundamentalism, as it is today in the United States, where 44 percent of people persist in believing that humans were created directly by God, not through any evolutionary process. In Darwin’s day, few believed in the literal interpretation of the book of Genesis, with its six twenty-four-hour days of creation. Rather, men and women worried that without God’s hand in the creation of human kind, life would be amoral, without meaning and purpose; we would be, then, no better than the animals. Darwin had avoided the topic of human origins in his Origin of Species, referring to human evolution only in very oblique terms: if his view is accepted, he blandly noted, “light will be thrown on the origin of man and his history.” But no one was fooled. As Bishop Samuel Wilberforce famously sneered to T. H. Huxley, known as “Darwin’s bulldog” for his vociferous defense of Darwin’s evolutionary theory, at the meeting of the British Association in Oxford in June 1860, “Are you related to an ape on your grandfather’s or grandmother’s side?” Huxley spoke for many, even those who opposed evolution, when he replied that “I would rather have a miserable ape for a grandfather than … a clergyman of the Church of England who introduces ridicule into a grave scientific discussion.”69
The members of the Philosophical Breakfast Club took a different approach. They each believed, as Babbage had proclaimed, “No truth in any department of knowledge can ever be in contradiction to any other truth.”70 Truths of science and truths of religion cannot conflict, even if we do not have full insight into how they coincide. If a scientific theory that is confirmed by the evidence seems to conflict with our interpretation of the Bible, then our biblical interpretation is faulty. As Whewell had put it in his review of Lyell’s Principles of Geology, “We do not conceive that those who endeavor to fasten their physical theories on the words of scripture are likely to serve the cause either of religion or science.”71 Neither Herschel nor Whewell believed that Darwin had proven that his theory of evolution by natural selection was true, but they—especially Whewell—saw that there was enough evidence to adopt a “wait and see” attitude. As Whewell admitted, in a private letter to his friend David Forbes, “I cannot see without some regrets the clear definite line, which used to mark the commencement of the human period of the earth’s history, made obscure and doubtful.… It is true that a reconciliation of the scientific with the religious view is still possible, but it is not so clear and striking as it once was. But it is weakness to regret this; and no doubt another generation will find some way of looking at the matter which will satisfy religious men. I should be glad to see my way to this view, and am hoping to do so soon.”72