Neo-Naturphilosophie A Review of Michael Ruse’s Gaia: Science on a Pagan Planet (review)

John Nelson, a cartographer and specialist in data visualization, has used NASA satellite photos of Earth to create animated GIFs in which the planet seems to breathe (Nelson 2013). Seasonal cycles are compressed down to moments, green turns to brown and back to green, and snow cover in the Northern Hemisphere expands and contracts rhythmically, at about the same pace as human breathing. It is hard to watch the animations and not come away with the impression that the planet is, in some sense, alive. Of course, we all know (don’t we?) that it’s not really alive. But Nelson’s work makes us wonder how our intuitions about this sort of thing might be influenced by spatiotemporal scale. If we could live our lives at a vastly larger spatial and temporal scale, would planet Earth seem just as obviously alive to us as any cell? Nelson’s animations dispose one to look more favorably on the Gaia hypothesis.

James Lovelock and Lynn Margulis teamed up in the early 1970s to defend and promote the Gaia hypothesis (Lovelock and Margulis 1974). Lovelock was a chemist and inventor with wide scientific interests who at the time was probably best known for developing the electron capture device. Margulis, a biologist, was known for her theory that eukaryotic cells first formed when some prokaryotes swallowed up others with which they had a symbiotic relationship. Together, Lovelock and Margulis argued that Earth is a self-regulating, homeostatic system. “Gaia” was their name for the living planetary organism.

Why did the broader, nonscientific public respond so warmly to Lovelock and Margulis’s idea, while much of the professional scientific community reacted so dismissively? In his new book, Michael Ruse explains the mixed reception of Lovelock and Margulis’s Gaia hypothesis by giving us an intellectual history. What Ruse offers is not just a history of science, but a history of ideas as seen from high altitude. Early in the preface, he tells us that this “is not really a book about Gaia. It is, rather, a philosophical and historical meditation on the nature of science itself” (ix). Ruse argues that in order to understand a scientific disagreement, you need to know something about the relevant history of philosophy, about the dominant metaphors, the state of play of other scientific debates at the time, past and present religious tendencies, and even the pseudoscientific ideas from which professional scientists are keen to distance themselves. This need for the big picture is a theme of much of Ruse’s work, and Gaia lends itself to this approach. Ruse, who is more sensitive than most to the complicated roles that metaphor plays in science, is the right philosopher for this particular job.

Ruse makes it clear that Gaia developed out of a relatively straightforward idea that’s both scientifically respectable and uncontroversial. Living things depend on certain aspects of the (apparently) nonliving environment, such as ocean and atmospheric temperatures, or the acidity of the oceans and soils. But living organisms, in the aggregate, also do all sorts of things that make a difference to their environmental conditions, giving rise to interesting feedback loops. To rehearse just one of several examples that Ruse canvasses: Living things affect the albedo of the earth’s surface. Ice and snow have relatively high albedo, meaning that they reflect more of the sun’s energy back into space, exerting a net cooling effect on the planet. Living organisms, such as trees, provide a lower albedo surface covering. Holding other variables fixed (and there are many other variables to consider), plants can have a warming effect merely by spreading to cover more of the planet’s surface. The albedo effect is just one way living things can make a difference to the abiotic environmental conditions that they depend on. Scientists continue to investigate the details of these biogeological feedback loops, and no one doubts their...