This is the ninth installment of an abridged version of my book Reef Madness: Alexander Agassiz, Charles Darwin, and the Meaning of Coral. Here we see, with some surprise, that the world’s most famous zoologist thought of himself, in his most crucial formative stage, as a geologist.
© David Dobbs, 2011. All rights reserved.
The Beagle trip made Darwin, forming his mind and giving him the material for most of his major works. He later called the journey (which took five years rather than two) “by far the most important event in my life.… I owe to the voyage [my] first real training or education” as well as the “habit of energetic industry and … concentrated attention.” He began the trip an unfocused idler and finished it a hard worker and penetrating theorist.
His wistful recollections of the journey also suggest that he later saw this period as the time he was most completely alive — still physically adventurous even as he first experienced the exaltation of deep intellectual engagement. His physical and mental exertions were linked more seamlessly than they ever would be again, for his fieldwork sparked an ongoing interplay of observation and abstraction. “Everything about which I thought or read,” he said of that time, “was made to bear directly on what I had seen or was likely to see.” This sentence describes precisely the loop of thought, observation, speculation, and reshaped thought that marks Darwin’s mature method. It is a method that puts thought first — ideation inspiring examination, rather than vice-versa — and weighs reasonable conjecture (“what I … was likely to see”) as heavily as actual observation (“what I had seen”). Every outing both shaped and was shaped by the theoretical framework taking shape in his head.
Darwin was introduced to this sort of thinking early in the Beagle voyage by another book that changed his life and thinking, Charles Lyell’s Principles of Geology. Reading the freshly published Volume One (of an eventual three) in his first days at sea, he thrilled to find an intellectual world opening in his head even as a new, corresponding physical world opened beyond the ship’s rail. “The Principles,” Darwin would write a decade later, “… altered the whole tone of one’s mind and thence when seeing a thing never seen by Lyell, one yet saw it partially through his eyes.” The influence was so great that “I always feel as if my books came half out of Lyell’s brain.”
This first volume of the Principles was a gift from Captain Fitzroy, and it was one Fitzroy later intensely regretted. The captain was so conservative a Tory that he had almost rejected Darwin for the ship’s naturalist post when he heard he was a Whig. He was also an evangelical Christian, and he was so appalled when Darwin published his evolutionary theory in 1859 that he became a vociferous and prominent critic. The tension from maintaining this very public opposition to his old friend helped drive him mad; in 1865, he killed himself by slitting his throat.
Darwin probably sensed Lyell’s Principles was seditious. Henslow, while recommending the book to him as interesting, had warned him not to believe it. He not only believed but reveled in it. “The very first place which I examined,” he wrote in the Voyage of the Beagle, “namely St. Jago in the Cape de Verde islands, showed me clearly the wonderful superiority of Lyell’s manner of treating geology.”
Darwin didn’t find only Lyell’s geology superior. He loved his imaginative approach to making sense of nature. Lyell pushed far ahead of his peers, alarming some while thrilling others, by rejecting both the prevailing catastrophist explanations of the earth’s features and the contemporary inductivist prohibitions against speculation. He insisted, in short, both on sticking to the facts and using them as springboards for bold conjecture. In doing so he at once confirmed and pushed ahead of the empirical tenets of his fellow British scientists.
Lyell’s break from catastrophist theory was sharp and explicit, and it liberated geology as thoroughly as Darwin’s evolutionary theory later liberated biology. Doubtless that explains some of its attraction to the young Darwin. The catastrophist geology taught during Darwin’s college days left him cold, for despite visions of flying rock, lava, water, and ice, catastrophist geology offered a static view of nature. It saw the earth as essentially nondynamic, with a stable order occasionally disrupted by huge, presumably divine cataclysms — global floods, immense volcanic eruptions, disturbances from passing comets — that had shaped its crust. The outbursts were exciting. But as the order was God’s, the forces driving these spasms needed little further explanation.
Lyell rejected that as no science at all. He insisted on explaining geologic history not by reference to divine act, but by means of natural causes presently in effect. This uniformitarianism, as Whewell would later term it, was really both a geologic theory and a wider scientific principle. The Principles‘ main geologic argument was that the earth’s features were formed over long periods of time by forces still in operation; it followed that one should explain geological phenomena by referring to causes demonstrably at work.
As geology, this uniformitarianism, or gradualism, would eventually be considered overkill; a twentieth-century “actualism” would reconcile it with a more natural catastrophism to allow for occasional natural events we’ve never directly witnessed but for which ample evidence exists, such as tectonic collisions, Ice Ages, and meteor strikes.
As a working principle, however, Lyell’s uniformitarianism cleared the way for science’s advance in profound and badly needed ways. For while the insistence that every theory use verifiable existing causes sometimes left science short of explanations for complicated or elusive phenomena, it made for more certain progress by preventing science from accepting idealist or catastrophist explanations. It forced empiricism. It was not enough to say an apple falls because God tossed it down; one must define and calibrate the natural force that makes the apple drop. You were required, in the schoolteacher’s term, to show your work. Of course, much of the most lasting science had always been done in this manner. But the indulgence of catastrophism allowed such empirical thinking to be set aside, and science to stagnate, whenever a natural cause proved too elusive or threatening. Uniformitarianism meant always seeking a natural explanation — even if it meant not finding one.
Lyell did not invent uniformitarianism. The British geologist James Hutton had first proposed it in his 1795 Theory of the Earth. But neither Hutton’s leaden prose nor a clearer 1802 explication by his friend John Playfair could unseat the catastrophist geology then being elaborated by Cuvier. Lyell had better luck. Cuvier died soon after Lyell’s first volume came out, for one thing. More important, British science had grown increasingly confident in its empiricist principles in the quarter-century since Hutton and Playfair. Finally, Lyell simply made a better case than Hutton had, demonstrating repeatedly over three volumes how it was not just possible but necessary, as his book’s subtitle put it, to “…explain the former changes of the Earth’s surface by reference to causes now in operation.” His book thus made the first successful case for what we now know as uniformitarianism or gradualism.
Principles similarly pressed another Lyellian innovation: He rejected inductivist taboos regarding speculation. This innovation posed more of a challenge to many of his British colleagues than did his uniformitarianism, for at the time, a cautious, gradual method of theory-building was de rigueur among British scientists. This strict inductive model — the insistence on moving slowly and carefully from the specific to the general — had originated in 1620 with Francis Bacon, who forged it to liberate science from the bonds of church, state, and errors of logic. Bacon outlined an elaborate process of inductive inference to replace the deductive approach that had been established by Aristotle two thousand years earlier. Aristotle’s deductive model called for juxtaposing two or more known truths to reach a third, as in the classic syllogism, Gods are immortal; humans are mortal; therefore, humans are not gods. Aristotelian deduction worked splendidly as long as you used sound premises. But it begged error and abuse. Obviously you could err if you used a false premise — if, say, you had somehow overlooked some mortal gods — for one false premise could produce many others that would in turn produce yet more mistakes. The method’s exposure to abuse had proven even more serious, for if someone could dictate which premises were to be considered true, the syllogistic method generated stasis. Thus astronomy was inhibited (to put it mildly) by the Catholic Church’s insistence that Earth was the universe’s center, and both geology and biology were long hampered by Christian dicta about the earth’s age and humanity’s origin. You would only get so far in astronomy, for example, if you had to use as a premise, “The universe orbits the Earth.”
To free science from these dangers, Bacon offered his slow, incremental inductivism. Here was a way to peg truth and theory to observable fact. It’s no coincidence that he worked in the wake of Martin Luther, who in the early 1600s had launched Protestantism by insisting that religious truth lay not in the Church’s authority but in the evidence of scripture. Bacon, also hoping to supplant authority with evidence, tried to design a scientific method that left nothing to leaps of faith, unsupported assertion, or unfounded supposition. Rather than work from untested premises or move from a few observations to an “illicit and hasty generalization,” the scientist would use observed particulars to slowly build a pyramid of “gradual generalizations” leading to broader theories or laws.
Bacon’s method quickly won great credibility in Britain. By the early 1800s it had been bolstered by the empiricist philosophies of Locke and Hume and the accomplishments, held to be reached in Baconian fashion, of Kepler, Newton, and other scientific giants. The tension between British inductivism and Germany’s idealist Naturphilosophie only deepened British allegiance to Bacon’s method. By the time of Lyell and Darwin, inductivism had become the rule of the day in the British scientific establishment; to deny you practiced it was to risk your credibility.
In 1830, however, the Englishman John Herschel, a respected member of the British scientific establishment because of his careful mathematics and astronomy, argued in his Preliminary Discourse on the Study of Natural Philosophy that too strict an inductivism needlessly hampered progress. In a lucid discussion of how scientific theories are formed and tested, Herschel held that it mattered little how you came up with a hypothesis — it could be an educated inference, a wild guess, or a dream — as long as you tested it rigorously against observation. One shouldn’t hold a theory’s creation to the same standards as its proof. Since a hypothesis was just a provisional explanation that required testing to become a legitimate theory, why should its genesis matter? Why couldn’t you leap to the top of the pyramid and then build the understructure, revising as needed? If a child joked that the sun was at the center of the solar system, wasn’t this as useful a hypothesis (assuming you tested it against observation afterwards) as a conjecture based on years of telescope work? The real test of either lay in measured observation; origin hardly mattered.
Herschel’s proposal stirred a long, uneasy controversy, for he had articulated a fundamental tension in the accelerating push toward empiricism. Did a primacy of the observable require that knowledge move from the particular to the general? Everyone agreed that a theory must not merely fit a few facts but stand in accord with virtually all available relevant observations and experiments. But must it rise directly from observations and experiment? Or must it merely agree with them once it was conceived? This debate would run for another century, expressed as much in people’s work as in their talk. Both Darwin and Alex would find themselves enmeshed in its labyrinthine difficulties.
Most of the actual published response came soon after Herschel published his Preliminary Discourse in 1830. The eminent empiricist William Whewell, for instance, objected sharply in his review, insisting that while scientists must use inference to form a hypothesis, those inferences should be incremental and rise from sober consideration of significant evidence. They could not be large deductions or leaps of imagination. The path from fact to theory must be one of many steps, not a jump over a gap that you backfilled later.
As Whewell was a man of immense intelligence, accomplishment, and influence, his review, as well as his arguments in conversation in London and at Oxford, did much to discourage acceptance of his friend Herschel’s argument. A decade after Herschel published his Preliminary Discourse, Whewell authoritatively elaborated his inductivist caution in his monumental, two-volume Philosophy of the Inductive Sciences of 1840, which built on his equally weighty History of the Inductive Sciences of three years before. In the 1837 History, Whewell had described how key scientific advances had been made. Now, in the Philosophy of the Inductive Sciences, he drew on that history to update and elaborate Bacon’s inductive method. He wrote — and at Henslow’s and other Cambridge gatherings, talked — all during the 1830s and 1840s on these ideas, which were given extra credibility by his brilliance, his voluminous reading, and his experience in mathematics, mineralogy, and tides.
Coming atop almost two centuries of inductivist tradition, Whewell’s deeply learned advocacy won the day and even the century. Throughout the 1800s, his neoBaconian approach remained the standard prescription for inductive method, especially among the British. Scientists might privately admit that they sometimes yanked ideas from the blue. But publicly they sided with Whewell rather than Herschel. Thus in his Autobiography, Darwin, though he named Herschel’s book (along with Humboldt’s) as one of the two that most influenced him, would claim that in forming his evolutionary theory he worked on “true Baconian principles.”
Lyell preferred Herschel’s model. In Principles he put it to work with unprecedented boldness, freely jumping to hypotheses about the earth’s crust and openly justifying the need to speculate. In a way he was simply making virtue of necessity, as replacing catastrophism’s miracles with natural forces sometimes required conjecture. But he did so unapologetically. He was happy to value observations not merely as facts to be accumulated incrementally but as springboards for imaginative conjecture. Once having leapt to a new idea, he would amass robust evidence to support his position. But he was not shy about having leapt to get there.
Lyell was also willing to argue through relevant analogy as well as direct evidence — another Herschellian idea that defied Bacon. This greater use of speculation and analogy made many of his colleagues queasy. Yet he used this method so productively and backed his assertions with so many observations that even those leery of his speculation agreed that he had greatly advanced geology.
For the young Darwin, as for many others, the effect was breathtaking. Lyell changed geology from an enumerative task to a quest engaging eyes, legs, intellect, and imagination; one saw both the earth and the possibilities of science in a new light. Geologizing before and after reading Lyell was something like the difference between simply hunting beetles and studying them with their evolutionary arc in mind. To be a pre-Darwinian beetle collector, as Darwin had been, was to gather bugs and fit them, unquestioning, in a stable, divinely designed system. Like finding and placing the lenses of a stained-glass church window, it gave a certain pleasure but ultimately only confirmed a prescribed order. In that sense, as Darwin wrote Henslow early in the Beagle voyage, “in collecting, I cannot go wrong.” Yet for Darwin, such work created no excitement beyond the hunt. He cared less for completing a prescribed vision than for sketching a new one. Thus thinking about beetle-collecting bored him, as did geology before Lyell.
Geology after Lyell was another story. Nothing, said Darwin, now matched the pleasure of hammering rock and pondering its meaning. “The pleasure of the first day’s partridge shooting or first day’s hunting,” he wrote his sister from Tierra del Fuego, “cannot be compared to finding a fine group of fossil bones, which tell their story of former times with almost a living tongue.” Geology had eclipsed even shooting. Looking over his time geologizing in South America, he wrote in his Autobiography,
I can now perceive how my love of science gradually preponderated over every other taste. During the first two years my old passion for shooting survived in nearly full force, and I shot myself all the birds and animals for my collection; but gradually I gave up my gun more and more, and finally altogether, to my servant, as shooting interfered with my work, more especially with making out the geological structure of a country. I discovered, though unconsciously and insensibly, that the pleasure of observing and reasoning was a much higher one than that of skill and sport.
It comes as a jolt, reading Voyage and Darwin’s letters from the trip, to realize that history’s most famous biologist began his career far more entranced with geology. His zoological and botanical collecting on the Beagle trip, he said later, were at the time valuable mainly for sharpening his powers of observation; it wasn’t until he returned to England that he began to see the evolutionary patterns in his zoological data. During the trip, he still saw zoology as just collecting. In contrast, “the investigation of the geology of all the places visited … was far more important, as reasoning here comes into play.” His Beagle field notes show clearly his enthusiasms: he took just 400 pages on zoological topics and some 1400 on geology. Of the five books he wrote soon after he returned, the three most technical and scientifically substantive concerned geology, as did part of a fourth that proved most popular. In 1839, as part of his obligation to the journey, he wrote a section of the official journey account, the Narrative of the Surveying Voyages of Her Majesty’s Ships ‘Adventure’ and ‘Beagle’, and also published the Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage Round the World of H.M.S. Beagle, which soon became a bestseller known as The Voyage of the Beagle. Much of the Voyage concerned geology, and his next three books focused on it exclusively — his coral reef book in 1842, a volume on volcanic islands in 1844, and one on the geology of South America in 1846.
Nothing excited him as much as geology did. Nothing so engaged his suddenly curious mind. The task of discerning the earth’s evolution gave a thrill, he wrote a cousin, “like the pleasure of gambling.”
Image: Patagonia, by < href=”http://www.flickr.com/photos/64512868noo/”>Fieltros de la Patagonia, via Creative Commons
Reef Madness Begins: Louis Agassiz, Creationist Magpie
Reef Madness 2: The One Darwin Really DID Get Wrong: Rumble at Glen Roy
Reef Madness 3: Louis Agassiz, TED Wet Dream, Conquers America
Reef Madness 4: Alexander Agassiz Comes of Age
Reef Madness 5: How Charles Darwin Seduced Asa Gray
Reef Madness 6: The Death of Louis Agassiz
Reef Madness 7: Alex Finds a Future
Reef Madness 8: A Dissipated, Low-Minded Charles Darwin
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