For many years, I taught an introductory philosophy class based on Plato's Republic. It is a wonderful work through which to bring students to some of the crucial issues that engage and divide human beings—the nature of knowledge, the desirability of democracy, the place of women in society, mathematics, and God. Above all, there is the Theory of Forms, extrasensory entities that are supposed to inform and determine the objects in this world of sensation and experience. They are Plato's answer to the challenge posed by two earlier thinkers: Heraclitus, who claimed that everything changes ("You cannot step into the same river twice."), and Parmenides, who claimed that nothing changes ("How could what is perish? How could it have come to be?"). The Forms are timeless and yet manifest themselves in this physical world of corruption and decay.
Others intent on the same ends as I was might have chosen different works by Plato, but I suspect that few if any would have seized on Timaeus, a rather odd dialogue (at least to us) in which Plato argues that the world is a giant organism fashioned by a God, the Demiurge. Today it's hard to imagine that in the early Middle Ages, until Thomas Aquinas and others discovered the attractions of Aristotle, Timaeus was the only known work of Plato. And very influential it was, too, as almost everyone in the early centuries of the last millennium agreed that the world was an organism of a kind. Hence, as with all organisms, it was appropriate to think of the world as having sensations and feelings, and also to ask questions about ends and purposes.
The coming of Aristotle did not stop that mode of thought—indeed, he emphasized that such end-directed thinking (what he spoke of as final-cause thinking) is an absolutely vital tool for understanding the world around us. As Carolyn Merchant, a professor of environmental history at the University of California at Berkeley, showed in The Death of Nature: Women, Ecology, and the Scientific Revolution (Harper & Row, 1980), even at the beginning of the 16th century, on the verge of great changes in our understanding of the world, it was considered appropriate to give thanks when, in order to extract minerals, miners cut into the earth—cut quite literally into our mother. It was thought necessary to respect the earth for what she was and what she gave. Crass misuse of her bounties was sinful.
At the same time, one could ask questions about the world that were (as with organisms) couched in terms of ends. Just as we might ask about the purpose or function or end of the eye, so we might ask about the purpose or function or end of (let us say) rain. And answers were forthcoming: The eye exists for sight. Rain exists for the growth of crops.
It is not silly to think of the world as an organism. After all, every year it goes through phases of growth, flourishing, yielding its fruits, and then withering and dying. In their fascinating new biography, James Lovelock: In Search of Gaia (Princeton University Press), the science writers John and Mary Gribbin introduce us to a man who endorses this metaphor with much enthusiasm.
The British-born Jim Lovelock (as they call him) is someone with a deservedly high reputation as a scientist. Although trained as a chemist, for many years (thanks primarily to the demands of the Second World War and its aftermath) he worked on biological and medical questions, investigating such matters as the spread of the common cold, a problem which involves the physics and chemistry of small particles as much as anything strictly organic in itself. By the early 1970s, that research had earned him a Fellowship in the Royal Society of London. Around that time, however, Lovelock broke from conventional science, having become convinced that the earth is a living organism. To this hypothesis, drawing on a suggestion by his neighbor—the late Nobel Prize-winning novelist William Golding—Lovelock gave the name Gaia, referring to the Greek goddess of the earth.
Gaia has gone through various formations and definitions—in his less-than-enthusiastic book this year The Medea Hypothesis: Is Life on Earth Ultimately Self-Destructive? (Princeton University Press), Peter D. Ward, a professor of paleontology at the University of Washington, traces several variations. Unfortunately, Lovelock himself is not always terribly helpful about the precise nature and content of his own claims. His latest book, The Vanishing Face of Gaia: A Final Warning (Basic Books, 2008), is not the place to start looking for answers, since it seems to be little more than clippings from the floor of a long career. Better to go to some of the earlier works, perhaps the first full declaration, Gaia: A New Look at Life on Earth (Oxford University Press), first published in 1979, although Lovelock had gone public with the idea in articles at least five years earlier.
Speaking of the new perspective on ourselves of looking at the planet from outer space, Lovelock writes:
We now see that the air, the ocean and the soil are much more than a mere environment for life; they are a part of life itself. Thus the air is to life just as is the fur to a cat or the nest for a bird. Not living but something made by living things to protect against an otherwise hostile world. For life on Earth the air is our protection against the cold depths and fierce radiations of space.
There is nothing unusual in the idea of life on Earth interacting with the air, sea and rocks, but it took a view from outside to glimpse the possibility that this combination might consist of a single giant living system and one with the capacity to keep the Earth always at a state most favorable for the life upon it.
Things are kept in balance because when something occurs to shift the natural order of things, then other things occur to compensate, bringing one back to the original state. Seizing on the fact that the earth's temperature remains pretty constant, despite the increase over the years of heat from the sun (25 percent, the Gribbins tell us, from the beginning of life on earth), Lovelock looked for, and found, the necessary feedback mechanisms. For instance, volcanoes produce carbon dioxide; as carbonic acid, it becomes part of the rock-weathering process and eventually ends up on the sea floor; in turn it is taken up by primitive organisms like algae; through evaporation it gets whipped up into the clouds, giving the earth cover from the sun; and so the earth cools; and on we go, cycle after cycle.
What we have here is a homeostatic system a notion that was popularized in the 1930s by the American physiologist Walter B. Cannon, although those with longer historical memories will find the idea remarkably reminiscent of the Victorian man of science Herbert Spencer's concept of dynamic equilibrium. The Gribbins claim Charles Darwin as a precursor to that kind of thinking, but I find their argument most unconvincing. Darwin was never into balances of nature and that sort of thing. He saw change as continuing and profound. To go back to our Greeks, whereas Gaia is Parmenidean, Darwinism is Heraclitean.
Of course, it is not only in that sense that Lovelock is out of tune with modern science. Picking up the story at the end of the Middle Ages, in the time span from Copernicus, at the beginning of the 16th century, to Newton, at the end of the 17th century, something major happened in what was then known as natural philosophy. The idea (the metaphor, if you like) of the world as an organism was increasingly rejected in favor of the idea or metaphor of the world as a machine. To cite the title of one of the greatest histories written about the period, by the Dutch historian E.J. Dijksterhuis in 1950, minds turned to The Mechanization of the World Picture.
Why did the new perspective triumph? Why did people want to drop all of that organiclike, end-directed thinking and focus instead on blind law, working with undeviating regularity? There is no great mystery here. It was not some violent repudiation of God. Copernicus was a minor cleric who died in good standing, and Newton, for all that he may privately have doubted the divinity of Christ, was an ardent—one might say obsessive—believer in a deity. The machine metaphor triumphed because it led to a science that more readily exhibited the values that scientists hold dear—Newtonian physics was more predictively fertile, more consistent, more unifying, more everything than Aristotelian physics. With the new physics you could explain and do things simply impossible with the old. A weapon maker could calculate the trajectory of a cannonball; a lens maker could work out the best kind of optical apparatus; a chemist could start to understand why certain combinations of elements work and others do not, saving valuable time and materials when making alloys.
The machine metaphor may have been regarded by the Aristotelians as akin to an Egyptian plague—there are those today who think likewise, especially the so-called "ecofeminists" who argue that we abuse and rape our dwelling place—but the current of thought did not sweep through overnight. At the end of the 18th century, Immanuel Kant notoriously declared that there would never be a Newton of a blade of grass, meaning that a machine-based picture could never fully capture the organic world. But in the 19th century, Darwin, thanks to his mechanism of natural selection, showed how organisms are subject to unbroken, unbending laws. Richard Dawkins, who has a gift for these sorts of phrases, spoke of organisms as "survival machines." And then, as the 20th century drew to an end, many believed that cognitive scientists had finally extended the machine metaphor to the human brain and its thinking abilities. We were invited to think of brains as the hard drives behind our thoughts—computers made of meat, said the computer scientist Marvin L. Minsky.
There have long been attempts to resuscitate the claim that the world is an organism. The most ardent were those by the German Romantics at the beginning of the 19th century—known as the Nature Philosophers, or Naturphilosophen—who included the poet Johann Wolfgang von Goethe, the anatomist Lorenz Oken, and the greatest advocate of all, the philosopher F.W.J. von Schelling. But generally, although those people often did good science, however you judge it, such attempts came to naught. The organic metaphor did not work as well as the machine metaphor. Indeed, the enthusiasm of the Naturphilosophen, and more particularly of their modern-day successors, does show why it was as well that, before Lovelock took up the organic metaphor, his fellowship at the Royal Society was already in hand.
To say the least, initial reaction to the Gaia hypothesis was not overly enthusiastic. Or rather, in respects, initial reaction was even worse than that, because the theory was enthusiastically embraced by the wrong people—joss-stick-burning, Eastern-religion-embracing, herb-consuming (eaten and smoked), Birkenstock-wearing, now-aging hippies and New Agers. Respectable scientists shunned Gaia. The notable exception was the American biologist Lynn Margulis, a professor of geosciences at the University of Massachusetts at Amherst, author of a brilliant hypothesis about the hybrid nature of complex cells (eukaryotes) from simple cells (prokaryotes). She is the exception that proves the rule. Not only is she someone with her own well-merited reputation for going against the mainstream—initially her cell hypothesis was derided and denied—but her thinking is deeply holistic in an organic way, seeing parts coming together to make living wholes that function only as complete systems and not as blind mechanisms built out of disparate bits and pieces.
Although I don't think of Gaia as in any sense a religious hypothesis—neither Lovelock nor Margolis promotes that cause—I can see the attractions for someone who thinks that a good God designed this earth of ours. Lovelock was for a time close to Quakerism, and, although he has moved on, he certainly has the holistic reverence for creation that one finds in that religion: "that of God in every person."
In science, unfortunately (or perhaps fortunately), niceness is not enough. There were some telling hits on the Gaia hypothesis. Scourge of all things sloppy—especially those with the odor of the quasi-spiritual—Dawkins, in his 1982 book The Extended Phenotype: The Gene as the Unit of Selection, argued that organisms are produced by natural selection, which requires reproduction, variation, and a struggle for existence. There is no reason to think that the earth has been produced that way, hence no reason to think of it as an organism. To which Lovelock (who did, to his credit, take the criticism seriously) responded (in books like The Ages of Gaia: A Biography of Our Living Earth, first published in 1988) that, on the one hand, he meant the organism talk in only a loose, metaphorical sense (which may have gotten him off the hook but made his claims rather less interesting), and on the other hand, for him the chief mark of life is homeostasis (which may have satisfied the physiologists and Spencerians but left the evolutionists and Darwinians a lot less than happy).
In major part, however, the objections to Gaia were more philosophical than scientific, echoing the earlier critics of Aristotelian thought, like Francis Bacon and Descartes. Thinking of the world as having ends, of volcanoes as having functions (spewing out carbon dioxide), goes against the spirit of modern science and is not very helpful. The argument that Gaia is unfalsifiable was also trotted out, starting with a letter published in Nature in 1990 from James W. Kirchner, an earth scientist at Berkeley, who has leveled this charge repeatedly. Again to his credit, Lovelock took his critics seriously. (Whatever you might say, this is a man who gives science the respect it deserves.) He came up with the "Daisyworld" model. Suppose you have a planet covered in flowers: black daisies that absorb the sun's rays but that like the cool, and white daisies that reflect the rays but that thrive in the heat. As the sun warms up, thanks to the black daisies, the planet gets warmer. Then the white daisies increase in number and reflect more rays back into space; the planet starts to cool. Eventually a kind of equilibrium is achieved. There is no strange teleology; no weird forces bringing the end about; all is mechanical. Yet there is homeostasis.
Critics have not been convinced. Ward, in The Medea Hypothesis, argues bluntly that our planet is not a Daisyworld. Drawing on his experience as a paleontologist, he says the history of the earth and its life suggests that there are violent fluctuations—especially mass-extinction episodes—and no evidence that the earth then returns to anything like equilibrium. Indeed, he argues (and that gives him his rather overly cute title, which refers to the character in the Euripides play who killed her children) that life is, in a sense, poisonous and carries within itself the seeds of its own destruction. For instance, again and again microbes in the sea have produced vast quantities of carbon dioxide, leading to violent changes of temperature here on earth, a consequent lack of oxygen, and mass deaths. There is nothing particularly homeostatic about any of that, even though there may have been rebounds to eras of very different flora and fauna.
I was surprised not to find some discussion by Ward of the work of the late J. John Sepkoski Jr. A paleontologist with sophisticated computer skills, Sepkoski spent much of his career mapping the rise and fall of groups of organisms, suggesting that it was less the external environmental influences that led to, say, the rise of flowering plants, or angiosperms, and more the ecological dynamics caused by the inventive exhaustion of certain organic forms and the arising of different forms that could create and take advantage of new niches. (The point being that there is only so much you can do with four legs. You need a new adaptation, like wings, which now let you exploit the air.) In a sense, Sepkoski's work seems not to fit comfortably into either a simple homeostatic model or one of violent death and destruction. Although he was well attuned to the brutal episodes in life's history, Sepkoski saw organisms as the ultimate determinants of this history. All of that, at a minimum, suggests that the true, overall picture may be more complex than either Lovelock or Ward suggests.
Lovelock and his critics agree that we cannot just go on as we are going on. The world in which we live is changing in a dramatic fashion, warming at a frightening speed. That is true whether because we have upset Gaia and taken her beyond her abilities to regenerate naturally, or because a Medea effect has kicked in and we are on the way naturally to another crash of the earth's life forms. We must do something.
Ever the discomfiting maverick, Lovelock himself is scathing about many of the proposals to replace our dependence on fossil fuels. Windmills in particular make him scornful; even with nonstop gales, we can achieve but modest gains. For him it is nuclear power or nothing. James Lovelock: In Search of Gaia has a jolly picture of him and his wife, in white coveralls, touring a French nuclear station. Ward is more inclined toward orbiting sunshades that would cut down on the amount of sunlight hitting the planet. Positioned over the oceans, they would reduce the growth of gas-producing micro-organisms. All a bit gloomy for sailors, one would think.
My sense is that Gaia has made an important contribution to our thinking about the planet, if only by virtue of the fact that it makes us think seriously about such issues as global warming and pollution of the oceans. As a historian and philosopher of science, I find that both Lovelock's theory and those of his critics inspire me to go back to the foundations of science and consider the root metaphors of empirical inquiry and why we prefer one set of models and ideas over another. It is true that as Gaia has been tamed (by Lovelock himself) into a more respectable notion in the light of modern science, it has lost some of its original dramatic appeal. No doubt those earnest Californians seeking spiritual backing for their enthusiasms will find other outlets.
As a Darwinian and a Heraclitean (and an ex-Quaker shunning his childhood roots), I confess that I am uncomfortable with balance and equilibrium, those Parmenidean conjectures. Although books like Ward's The Medea Hypothesis—so obviously written for the trade market, so selective in the evidence they use to make their case —make me no less uneasy. Perhaps in the end, Plato had it right: We need both perspectives, Heraclitean and Parmenidean, to get the whole picture. At our peril, and at our children's peril, we ignore the messages of those seminal Greek thinkers.