The Cave and the Light

by Arthur Herman

  As he pored over his notes and other examples from other naturalists, Darwin saw the same history being replayed again and again. Enough of one species survive to propagate the species, while others of another do not—while still others manage to branch off to generate entirely new species. Very suddenly, the phenomenon of shared characteristics also made sense: as the trace of a common ancestor, some of whose offspring lived to carry forward the variations (like men with nipples and bugs with wings) while the rest faded away.

  Thus the similarities between lizards and crocodiles; jaguars and tigers; men and the higher primates—between mammals of every description. Indeed, all life, he wrote in his notebook, “animals, our fellow brethren in pain, disease, death, suffering, and famine—our slaves in the most laborious works, our companions in our amusements—they may partake our origin in one common ancestor—we may be all melted together.” The reason all mankind is one, in short, is that all nature is one.38 Darwin had answered the why of evolution—at least in his own mind. The how came to him a year later in 1838, when he was reading a book by clergyman, amateur scientist, and economist Thomas Malthus titled An Essay on the Principle of Population, for “amusement,” Darwin said—meaning not as part of his own research. Malthus had written on the higher mathematics of the progress of civil society, or what Malthus feared might be its inevitable lack of progress. His twin starting points were that man’s ability to reproduce himself expands at a geometric rate, while his ability to feed himself from cultivatable land can grow at only an arithmetical rate. At some point those two lines must intersect, at the expense of everyone’s need to eat.

  Suppose my wife and I own a farm, Malthus was saying. Our children have their children, who in turn have theirs. We all set to work to bring more land under cultivation to feed an ever-growing number of mouths. The more they eat, the longer our children and grandchildren live, the more they prosper, and the more they multiply. Eventually, their numbers grow so fast that no matter how much land we put under the plow, there’s never enough to feed everyone. Starvation sets in; the new offspring die, as do the old; the fields fall fallow. Prosperity is at an end.

  Erasmus Darwin and his fellow optimists were wrong, Malthus argued. The power of propagating the species is the enemy, not the friend, of progress. Civil society will be doomed unless it finds decent ways to restrain our natural tendency to have more and more children. Otherwise, Malthus warned, we are doomed to a constant “struggle for existence” that will pit rich against poor, haves against have-nots, in ruthless competition for ever scarcer resources. If history is class struggle, Malthus suggested, it is because biology by the numbers makes it so.39

  The title of An Essay on the Principle of Population referred to human populations. But it occurred to Darwin that its strictures might also apply to other kinds of populations. Malthus believed men multiplied faster than food. If that were also true of animals or even plants, then they too must compete to survive. “It at once struck me,” Darwin remembered, “that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed.”

  “Tend” was the key word. Not every weak link dies out, nor do all those favorably fitted to circumstance flourish. However, enough do to form a new species—and to launch nature’s tendency to endless variation in a new direction. “Here then I had at last got a theory by which to work,” Darwin wrote in his Autobiography.40 He finally had his how, which he called natural selection.‡ His disciple Herbert Spencer coined a more portentous phrase for it, survival of the fittest, although survival of the adaptable would have been more accurate. Those who can adapt to the current environment, whether we’re talking turtles or wheatgrass or people, live to propagate and continue the species. Those who can’t, won’t.

  Natural selection became one of the most contentious parts of Darwin’s theory of evolution, in part because of its source.41 However, Darwin’s unexpected move was not in relying on Malthus’s law of population; it was in turning it from a barrier to progress into progress’s driving engine. Natural selection at long last solved the problem of what was the underlying structure of all natural history—indeed of life. For Darwin, the process is the structure. He had turned nature’s most obvious characteristic, its propensity for change, into its greatest virtue.

  That was still not the most controversial part of Darwin’s theory of evolution, and he knew it. It took him four years to write any of it down. In 1842, he wrote a draft of thirty-five pages in pencil; in 1844, he expanded it to two hundred. He showed it to no one. He set aside some money and some instructions for his wife on publishing it if he died (he was only thirty-five). It was not until 1858—when his friends Charles Lyell and Joseph Dalton Hooker arranged for a paper by Darwin to be read to the Linnean Society in London at the same session as a paper by Alfred Russel Wallace, who proposed almost the exact same theory of evolution—drawn from a similar trip to South America and from the same sources, including Malthus—that Darwin’s hand was finally forced.42 A year later, he published On the Origin of Species. The debate and controversy have not died down since.

  What made Darwin so reluctant to reveal his theory in public, and why did it win almost as many opponents, both in and outside the life sciences, as it did adherents? Certainly Darwin, who was a religious agnostic, knew it spelled the doom of the age-old creation story of the Book of Genesis. In fact, to this day the conflict over evolution is defined as a clash between Darwinists and so-called Creationists. Yet the history of geology has exposed the intellectual inadequacies of the seven-day creation story far more decisively than evolution has, and before Darwin arrived on the scene. His own theory depended on it. Yet it is Darwin, not Charles Lyell, who is the recurrent object of wrath and loathing.

  Is it because Darwin proposed that human beings were descended from higher primates? That claim, which Darwin developed in The Descent of Man in 1871, certainly raised plenty of ire at the time and since—and not just among dyed-in-the-cloth evangelicals. The entire foundation of Romantic liberalism, not to mention the Thomist position of Las Casas and others, was that man is part of nature but also above nature, because of the spiritual essence of his soul.

  No such immanent divine spark survives Darwin’s evolutionary logic. In fact, Darwin made a joke of it back in 1838 in his notebook: “If all men were dead, then monkeys make men, men make angels.” Man thinks himself a great work, he wrote, worthy of being created by a deity. “More humble and I believe true to consider him created from animals.”43

  This was a position more extreme than anything eighteenth-century Deists like Voltaire or Thomas Jefferson might have assumed. It also gets us closer to the truth about the opposition to Darwin: not because of what evolution says about men, but because of what it says about God. The traditional Western notion of God as Supreme Creator rested not only on Genesis but on Plato’s Timaeus, implying that the cosmos is a deliberate copy of divine perfection. This is especially true of man, who, as Christianity had argued from its start, had been made in God’s image—with all the force that Plato’s theory of Forms could give that statement.

  Now Darwin was implying that we are not the copy of anything perfect or divine. We are just one more set of beasts roaming the planet equipped with our natural reason as our only distinguishing mark. This didn’t just topple the foundation of Christian moral teaching and metaphysics; it meant that one entire half of the traditional Western worldview, the Platonist half, had to come crashing down from heaven to earth.

  Darwin knew what he had done by overthrowing the notion that Nature’s God creates according to a model of foreordained perfection. “But how much more simple and sublime [a] power,” he wrote in his notebook, “let attraction act according to certain law, such are inevitable consequences—let animals be created, then by the fixed laws of generation, such will be their successors.” Darwin’s God (assuming he had one) may not look like Plato’s or Saint Paul’s very much, but it does bear a family resembla
nce to Aristotle’s.44

  Aristotle had been as obsessed with perfection as his great teacher—witness his views on astronomy. But he was also willing to shrug and say: Look, if it exists, there must be a reason. In Aristotle’s mind, viewing the world as a copy of anything—even the mind of God—gets us nowhere. It is arguable whether Aristotle even had a conception of a God, but he did have a Prime Mover without whom nothing else moves.

  Aristotle also said that if something exists, then it must change, including the cosmos itself. Only the Prime Mover does not. Only He is unmoved, eternal, and perfect. The rest of reality is bound to the laws of nature: doomed, in other words, to various states of imperfection. That’s what makes it reality. And if evolutionary change is the rule for the rest of the cosmos, then why not for man himself?

  Aristotle’s God is not a caring god. His nature is pure actuality (energeia) and excludes all possibility of Him worrying about the creatures of the cosmos, let alone desiring any outcome. However, without Him the potential dynamism of matter would remain untapped. Wrapped in eternal self-contemplation, He summons up by His mere presence the latent powers of nature. God does not go out to the world, but the world cannot help reaching out to Him.45

  Even though Darwin pulled down the Judeo-Christian Neoplatonist framework of nature—not just Genesis but the Timaeus—we are still left with some firm metaphysical ground. A new way of understanding the universe appears. It is one closer to Aristotle’s, of a constantly changing but rational order embedded in eternity without beginning or end on any meaningful scale we can recognize, but of which we have no choice except to be part.

  There may be no Genesis or redemption. But when we examine the 1-billion-year remnant of rock shale or a 1.2-million-year-old Neanderthal skull, when we watch a butterfly emerge from its chrysalis or witness a supernova, we can say with Aristotle, “That is God thinking.”

  * * *

  * This was the law of decreasing magnetic intensity, a band that circles the globe roughly in the vicinity of the equator.

  † The interpretation of the crucial passage (in chapter 5, 1245a21–1245b32) is ambiguous. Some modern scholars like R. Schlaifer in Theories of Slavery from Homer to Aristotle insist that “Aristotle in no place clearly indicates how a true slave may be known from a free man.” Sepúlveda (who had published a translation of the Politics in 1548) believed otherwise. For obvious reasons, many Spaniards were ready to accept the authority of Sepúlveda’s Aristotle against any other reading.

  ‡ The word evolution, by the way, never appears in any of his notebooks or preliminary sketches for Origin of Species or in its first printed edition.

  Twenty-six

  UNSEEN WORLDS: PHYSICS, RELATIVITY, AND THE NEW WORLD PICTURE

  The true Logic of this world is the Calculus of Probabilities. This branch of Math., which is generally thought to favour gambling, dicing, and wagering, and therefore [to be] highly immoral, is the only “Mathematics for Practical Men.”

  —James Clerk Maxwell, c. 1859

  Such an interpretation of the properties of matter appeared as a realization, even surpassing the dreams of the Pythagoreans, of the ancient ideal of reducing the formulation of the laws of nature to considerations of pure numbers.

  —Niels Bohr, Nobel Prize speech, 1921

  After completing his manuscript of Das Kapital, Karl Marx could lay down his pen with no inkling that his universe was about to collapse.

  Not his political and social universe: that was precisely what he was hoping and planning for. The wave of upheaval, crisis, revolution, and war that engulfed Europe in the century after 1867 would have been his element. Even the two world wars coming in the next century would only have fed Marx’s appetite for apocalyptic destruction.

  Instead, it was his physical universe that would was about to be overturned. It started with his own desk.

  As Marx rubbed his fingers along its surface, he would have felt its rough wooden grain and its hard solidity—like the solidity of the other dark mahogany Victorian furniture scattered around the room. Rising to his feet, he would have heard the floorboards creak beneath him. He would have glanced at the pictures on the wall and the books on the shelf, and smelled the boiled potatoes as his wife made supper in the kitchen.

  Outside Marx could see people passing by, and carts and horses. In the distance would come the sound of a train driving along its iron tracks with powerful clockwork precision—driven by the same physical laws that powered the factories and foundries of Europe, that governed the growth and movement of the birds and animals and plants Darwin had described (Marx was a keen admirer of Darwin, whose laws of natural selection had a strong impact on his own thinking), and that brought out the moon and stars overhead when darkness fell.

  Or so it seemed.

  Every day everything Marx saw confirmed what he, and virtually everyone in mid-Victorian Europe, believed: that they lived in a solidly material world, securely made up of things and persons and events known through the experience of our senses. He had even called his theory of history dialectical materialism, on the grounds that it was matter that mattered, and physical matter—not ideas or spiritual or unseen entities—that was the only touchstone of reality and truth.

  This was Newton’s world as well. His mathematical laws of motion and gravity, which defined all physical cause and effect, were themselves defined by the immutable absolute dimensions of space and time. Matter, Newton wrote, was “solid, massy, hard, impenetrable … no ordinary power being able to divide what God Himself made one in the first creation.”1

  For the next two hundred years, even religious thinkers and theologians came to accept those material laws as the final fruit of science, and the final ground rules of all common sense. David Hume and Immanuel Kant doubted we could ever really get to know that material reality, what Kant called the thing-in-itself, directly. They were resigned to the fact that it could only be known through perception, what others would call sense data. But no one since Bishop Berkeley doubted that this material reality was actually there. And no one since Newton, not even Marx, ever doubted that it was governed by the laws set forth in his Principia.

  Yet in 1867, Scottish physicist James Clerk Maxwell was completing a series of computations that would start the process of throwing this entire Newtonian universe and its most basic assumptions, including the nature of matter, into upheaval. Everything defined as “the real world” since Aristotle was about to be rocked on its foundations—with Plato and especially Pythagoras looking more right than wrong.

  Maxwell grew up near Dumfries, in southwestern Scotland, in a family of down-at-heels but well-to-do eccentrics. It was said his grandfather once saved himself from drowning in India by floating down river on his bagpipes, then chased away marauding tigers at night by playing away at the pipes until he was rescued.2 His grandson loved puns and puzzles as well as geometry and mechanics; and after graduating from Cambridge in 1854 and teaching for a time at the University of Aberdeen, he withdrew to his family’s run-down estate to take on one of the major scientific puzzles of the age; whether light was a wave or a particle.

  Ever since Newton’s study of optics disclosed the existence of the spectrum, speculation on the question had raged. Maxwell’s research led him to conclude finally that it was a wave, and from there he went on to tackle two other phenomena that had fascinated the eighteenth century: electricity and magnetism. Maxwell was the first to demonstrate that both in fact formed a single field and obeyed the same laws, which he set forth in four simple but epoch-making mathematical equations. Using those equations, he was even able to compute the actual speed of light at 186,000 miles per second—that is, fast enough to circle the earth seven times in a single stroke.3

  All this would have been enough to win him scientific immortality, but Maxwell pushed further. He began arguing that light itself was an electromagnetic wave and that its visible spectrum, from red to violet, was only a small portion of a much bigger field of invisible el
ectromagnetic radiations. These ranged from very long ones, which came to be called radio waves (the existence of which Heinrich Hertz confirmed twenty years later, in 1888), and very short ones, namely X-rays (later discovered by another German, Wilhelm Röntgen, in 1895).4

  In short, here was an entire range of scientific phenomena invisible to the senses but obeying exact mathematical laws. Indeed, Maxwell’s theory of electrodynamics was not unlike Newton’s theory of gravity, but with a crucial difference. These laws existed not as equations on a chalkboard but as statistics in a table. Maxwell showed this when he took his theory to the study of gases and heat, and a theory propounded by Rudolf Clausius that heat was actually the result of kinetic motion of tiny bodies or atoms inside those gases. Maxwell postulated that the laws governing their motion could only be uncovered using statistical probability. Here he was thinking about the famed Gaussian bell curve, named after mathematician Carl Friedrich Gauss (1777–1855), which showed how serial observations or measurements—like the heights of a cluster of trees and speeds of a street full of cars—tend to bunch up around a standard distribution, with a few being very tall (or very fast) and a few very short (or very slow), and the rest grouped somewhere around the middle.

  It was an astonishing idea. Since Aristotle had first stated that “the fact is the starting point” of all knowledge, it had been assumed that exactitude was the sine qua non of all scientific truth. We want to know how this planet or comet travels through space, and exactly at what speed; we want to know at exactly what temperature this bar of iron reaches its melting point, and under what specific conditions. The whole advantage of applying mathematics to the study of chemistry or astronomy is that it enhanced that sense of exactitude—even put the final seal on it.