But then Las Casas went further. He knew he could not refute every instance of human sacrifice or cannibalism that had so shocked the Spanish conscience (compared with, say, burning people at the stake). So he showed that these actions were rational in the cultural context in which they had taken place. For example, since life is man’s most valuable possession, the fact that the Indians practiced mass human sacrifice showed a veneration for the divine far beyond any felt by ancient Greeks and Romans.20 Likewise, Spanish women could learn something, he suggested, from the devotion Aztec women showed to the education and welfare of their children, even though its content was very different. In their own time and place, then, the native Americans clearly met Aristotle’s criteria of rational human beings capable of virtue. Therefore they deserved to be left alone to govern themselves—and certainly not to be treated as slaves.
The Valladolid council adjourned without reaching a final decision. Perhaps not surprising, Spanish rule went on as before. But Las Casas’s arguments marked a turning point in the evolution of the Western mind.
It was a new way of seeing others who are culturally different: not as irrational or savage creatures deserving contempt or conquest, but as people like ourselves dealing with universal needs and desires in their own way. “All the peoples of the world are one,” was Las Casas’s final pronouncement, meaning they all share one nature. That nature rested on man’s reason, the one characteristic that all human beings share regardless of where they live. Underneath the wide diversity of societies, from the most primitive to the most advanced, was a single common human nature addressing the same problems in the same way but with different results, because of differences in the physical and cultural environment.
“Thus mankind is one,” Las Casas had told the king and his bishops, “and no one is born [superior and] enlightened.” From this it follows, he explained, that “the law of nations and natural law apply to Christian and Gentile alike, and to all people of any sect, law, condition, or color without any distinction whatsoever.”21
All mankind is one. It took a long time for this revolutionary argument, with its inheritance from Aristotle and Thomist doctrine, to gain firm purchase in the West. In the age of Atlantic empire and the Middle Passage, when shiploads of black Africans were being sent to the Americas, Europeans’ instincts and self-interest ran very much the other way. Nonetheless, the nagging doubt that had triggered the Valladolid debate in the first place remained. By what right did one race of men enslave another race, Europeans continued to ask (if only in whispers), when they shared the same rational nature?
The ultimate answer was, none. Interestingly, the final, decisive piece to the puzzle was supplied by Rousseau. Everywhere men are born free, he had written, yet are everywhere in chains. That meant that no one was destined to wear chains, whether they were white Europeans or black Africans, the archetypal “noble savage.” The same men who led the Reign of Terror abolished slavery in France. In England, opposition to the slave trade became one of the hallmarks of English Romanticism. Both Turner and Blake were sickened by it and used their artistic skill to portray its horrors. Writers like Shelley, Coleridge, and Wordsworth joined forces with Christian evangelist William Wilberforce to get it outlawed.
Alexander von Humboldt stood foursquare with them, for the same reasons. He wrote: “We maintain the unity of the human species [and] at the same time repel the depressing assumption of superior and inferior races of men.… All are in like degree designed for freedom.”22 Designed, that is, by Nature herself: a point that brought together all the different strands of thinking about cultural difference. Now it turned out our physical and moral makeup is only one aspect of a larger creative system.
Las Casas and the Thomists had pointed out that nature was the physical frame where over time man reveals his fundamental rationality. He does this first of all through his contemplation of nature, which leads him to infer the existence of a divine Creator, or what the Enlightenment called “natural religion.” He does it secondly through his actions in nature: his reshaping of his physical environment to suit his own needs and desires, including his natural desire to live with others: what the Enlightenment had dubbed “the progress of civil society.”
In the end, all these developments flow from the same source, man’s reason as a work in progress. “All men are equally made in the image of God with a mind and reason,” as Cardinal Bellarmine had said; which was epitomized by that supreme act of reason conquering nature, the acquisition of property. It also reflected the basic point Thomas Aquinas had extracted from Aristotle some six centuries earlier. Man is above nature but also part of it: he is subject to the same laws, both morally and physically. But do things work the other way? If it is part of man’s nature to change things for the better, then perhaps it is true, at least to some degree, of Nature herself.
Probably the first person to seize this insight was Erasmus Darwin, born in Derby in England in 1731. He took his first name from the sixteenth century’s most famous humanist and gave his surname to the nineteenth century’s most famous scientist. Unlike his future grandson, however, Erasmus Darwin was a portly, boisterous extrovert. A doctor by training, he took almost as much relish in man’s achievements in science and technology—the industrialist Matthew Boulton was one of his closest friends—as he despised organized Christianity and the institution of slavery. Dr. Erasmus Darwin saw man’s place in physical nature as something to be celebrated rather than glossed over. The human life cycle from helpless childhood to rational manhood; the spread of cultivated fields, great cities, and productive machines across the landscape: All reflected a dynamic system of improvement embedded in Nature herself, as well as society, which he dubbed evolution.
Evolution is a true Aristotelian concept, even if the term is not.23 Aristotle had argued that all change in nature was the prelude to completion, even fulfillment. Aristotle, however, was thinking of the development of individuals within a species, like our old friend Rover the Lab retriever, whose growth over time reflects the transformation of potentiality into actuality. Aristotle spurned any notion that species themselves changed over time, any more than did the planets in the heavens.
Erasmus Darwin was the first thinker to use the concept of evolution to describe nature as a whole.24 Everywhere he looked in 1700s England and Europe, the good doctor saw a ceaseless, ever-expanding process of birth, growth, and death in which every species—including man—expresses the potential for unlimited growth and improvement.
The heady prospect made him burst into poetry:
Shout round the globe, how Reproduction strives
With vanquish’d Death—and Happiness survives;
How Life increasing peoples every clime,
And young renascent Nature conquers Time.25
But exactly how did this renascent Nature end up producing all this Happiness? What is the engine (as his friend Matthew Boulton might have said) that powered its growth and improvement? In the case of the progress of civil society, it was man’s reason. Man’s mind led him to constantly improve his physical environment, whether one is talking about the steam engine or the Parthenon—or the temples at Taxlala and Machu Picchu, Las Casas would add, and the Iroquois’s wigwam and the Eskimo’s igloo. Indeed, it was that same invincible reason that led men to see the processes of nature as a whole.26
So what is it that triggered Nature to do the same? That was the question Erasmus Darwin and his great French rival, Jean-Baptiste Lamarck, could not answer. They left it to Darwin’s grandson to find it in the same place where Alexander von Humboldt had first plunged into the Book of Nature: in the lush jungles of South America.
“I was a born naturalist,” Charles Darwin said later. If so, none of his family or teachers noticed it. They saw instead a rather dull and lazy boy. “I was considered by all my masters and by my father,” he admitted in his Autobiography, “very ordinary, rather below the common standard in intellect.” He did badly at Greek and Latin, the
bread and butter of education in his day. Whatever he learned of Virgil or Homer “was forgotten in forty-eight hours.” One day his despairing father said, “You care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and your family.”27
What Charles Darwin really enjoyed were long walks alone or with friends, sometimes covering thirty miles in a single day. On the way, he collected odd bits of minerals and strange-looking bugs (his sister convinced him it was wrong to kill insects for the sake of collecting, so he gave it up) and became particularly absorbed in watching birds, making precise notes about their songs and plumage.
Although he earnestly studied chemistry—at school his nickname was “Gas”—and found Euclid’s geometry a stimulating read, Darwin saw nothing in the science of his day to attract his passion. When his father sent him to medical school at Edinburgh, he found the subjects as uninspiring as the professors were dull. He read his grandfather’s Zoonomia, which anticipates so much of Charles Darwin’s later thinking, with admiration. But on a second reading, “I was much disappointed; the proportion of speculation being so large to the facts given.”
It wasn’t until he arrived at Cambridge, ostensibly to study theology, that Darwin found two books that would change the direction of his mind and the focus of his life. One was Humboldt’s Personal Narrative. The other was a book by Herschel, wordily titled Preliminary Discourse on the Study of Natural Philosophy. It powerfully suggested that the natural sciences could still gain what everyone said they lacked most, namely a systematic basis for certainty.
Herschel was an astronomer and physicist. He was the son of an even more famous astronomer. Picking up his book, Darwin must have expected him to treat mathematical laws as the be-all and end-all of true science. But surprisingly enough, Herschel didn’t. The face that appeared on the book’s title page was not that of Newton but that of Sir Francis Bacon; and the entire book was about the power of observation and practical experiment to generate a provisional explanation, or hypothesis, which, once we add more observations to either confirm or deny our hypothesis, gradually solidifies into a general law. That law, Herschel admitted, might not be mathematically precise—or at least not at first. But once it’s tested by time and dint of example, it can be enough to explain what’s going on.
The key was finding a provisional link between cause and effect. “I gave both the dog and the cat some vitamin D,” the experimental scientist says to himself, “and both their skin rashes went away.” This discovery leads him to make a hypothesis: Whenever an animal with a skin rash is given this amount of vitamin D, it will be cured. He will be able to reexamine old cases—“I saw a dog the other day eat some broccoli and its skin rash disappeared, so broccoli must contain vitamin D”—and open the way to considering new ones. When he gives vitamin D to his spouse and her skin rash actually gets worse, he doesn’t throw up his hands in despair. He wonders why vitamin D works for animals but not for humans and launches his research on a new line of investigation.
Reasoning in science, like reasoning in real life, is a process. It is, as Herschel showed, an inductive process. His book had a big impact on John Stuart Mill, who recast his system of logic to accommodate Herschel’s inductive, observational theory of science. It also had an impact on Darwin the would-be naturalist. Herschel made him realize that Humboldt’s travels in South America that had fired his imagination so much were about more than breathtaking vistas, exotic animals, and romantic tropical sunsets. Herschel had shown how a system of classification like Humboldt’s natural history could be turned into a framework for grasping the causal laws of nature that governed its operations.
Another scientist, William Whewell, offered an additional perspective. Induction, the patient gathering of data and the teasing out of causal factors, was clearly important to scientific research. However, the big breakthroughs, Whewell argued, required the more powerful force of the imagination. It was these inspired intuitive leaps, akin to those of a great painter or writer, that allowed “a genius of a Discoverer” like Galileo or Newton to suddenly sort our ordinary perceptions of things into an extraordinary and meaningful pattern—including our perception of living nature.28
It’s not clear whether Charles Darwin dared to think of himself in those terms, as a biological Michelangelo. But when he set sail in HMS Beagle on December 27, 1831, all these elements—the idea of the scientist as imaginative genius, Aristotle’s view of nature as change and process, and Humboldt’s Romantic vision of biological nature and humanity as one—were about to come together in a great shattering climax.
The trip itself was anticlimax. It turned out that Charles Darwin, who had not been to sea before, suffered from torments of seasickness. “I loathe, I abhor the sea and all ships which sail in it,” he wrote to his sister, “I hate every wave of the ocean.” The Beagle’s captain was all too happy to leave his miserable passenger on land for three or even six weeks at a time, while the Beagle completed her work of drawing up hydrographic charts on the South American coast. Darwin would spend almost four-fifths of the five-year voyage on land, gathering specimens, walking, watching, and thinking.29
That suited Darwin. Humboldt’s vivid descriptive prose had not prepared him for the lush scenery of green-carpeted mountains and volcanoes and hundreds of insects and birds of species he had never known before. It was like “giving a blind man eyes,” he wrote in his journal. “He is overwhelmed with what he sees and cannot justly comprehend it. Such are my feelings and such may they remain.”30 Darwin watched the flights of strange butterflies, examined volcanic outcroppings, and dislodged fossils from sedimentary rock. He met the natives of Tierra del Fuego, who had never seen white men and whose fierce appearance and bizarre folkways put his belief in the unity of mankind to a severe test.31
He saw the same giant sea turtles Humboldt had seen on the islands of the Galápagos (turtles so large, he noted, that a team of six men could barely lift them), and the strange lizards, each more than two or three feet long, which dotted the black lava rocks like “imps of darkness.” He also estimated there were at least twenty-eight species of land birds, almost all previously unknown, that lived in the Galápagos and nowhere else on the planet—a point that would figure prominently later in his theory of evolution.32
At the time, however, it was the geology of the places he visited that interested him most. He noted the long, slow transformations of the landscape due to volcanic activity and sedimentation, and shifts in the earth’s surface, all of which confirmed geologist Charles Lyell’s theory that the history of the earth was one of constant change and gradual upheaval. Darwin thought about devoting his time to writing a book on geology when he returned to England in 1836. A book on biology was far from his mind—certainly not a pathbreaking work like Origin of Species.33 However, what he had seen of birds and butterflies, tortoises and fossils, did puzzle him enough to start him leafing through his notebooks as he prepared the natural history volume for the official account of the Beagle’s voyage. Darwin began by asking himself the classic Platonic question that every great thinker asks: Why?
“Why is life short?” He wrote. “Why does [the] individual die?” Then he asked himself: Why do so few of so many individuals of animals or plants survive, yet just enough to perpetuate their species? Why do offspring resemble their parents, yet with enough differences to be distinct? Most crucially, why are some species so different from others, like tortoises and finches, yet so similar to still others? And finally, why do some species perpetuate themselves while others die off? “If [the] individual cannot propagate he has no issue—so with species.”34 How did nature make that ultimate selection?
Then very suddenly, in the spring or early summer of 1837, Darwin had the answer. His comments on the data in his notebooks show a new confidence and a sense of direction. He realized it meant chucking the idea that life on earth began at an act of deliberate creation such as the one described in the Bible—or in Plato’s Timaeus. If t
hat had been so, then men would not have been born with nipples (a puzzle that particularly fascinated Darwin). Unlike those of women, male nipples serve no possible purpose foreseen in the mind of a Creator. Instead, they must be a trace of a prior state when they were of use, Darwin decided, which had since disappeared from the human species. “So with useless wings under elytra of beetles. Born from beetles with wings, and modified”: modified not by a Creator, but by the passing of generations, which bring with them a constant, inexorable process of change.35
What Darwin had discovered was a way of seeing nature as an endless chain of mutability of species, reaching back through time to the very origins of life. On one side, Darwin’s theory was a leap into an unknown future; on the other, it was also a sharp glance backward. It revealed that Aristotle’s notion of a “scale of nature,” a continuous ladder made up of living things leading from the lowest to the highest order, was not so wrong after all—nor was Darwin’s grandfather’s picture of propagation as a process of self-renewing improvement and perfection.36
The problem with Aristotle, whom Darwin described as “one of the greatest, if not the greatest, observers who ever lived,” was that he had assumed that the species that made up this scale of nature, from the lowest plants to man himself, were fixed because the changes within species come so imperceptibly slowly, just like the geology of the earth.37 In fact, as fossils showed, species change all the time in the sense that some die off while others carry on. Even among those that carry on, individuals vary—a variation they are poised to pass to their offspring.
Each individual man or dog or mosquito, then, has the potential to alter the species or, given enough time to perpetuate enough variations, launch a new species itself. In short, the scale of nature is actually geared away from fixity of species, as Aristotle had wrongly assumed, and toward ceaseless variation. And what was true for one species, Darwin decided, must be true for entire classes of mammals and vertebrates and the entire range of living animals.
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