The idea of Gaia—of life on earth as a self-sustaining natural system—is not a gratuitous, semi-mystical fantasy. It is a really useful idea, a cure for distortions that spoil our current world-view. Its most obvious use is, of course, in suggesting practical solutions to environmental problems. But, more widely, it also attacks deeper tangles which now block our thinking. Some of these are puzzles about the reasons why the fate of our planet should concern us. We are bewildered by the thought that we might have a duty to something so clearly non-human. But more centrally, too, we are puzzled about how we should view ourselves. Current ways of thought still tend to trap us in the narrow, atomistic, seventeenth-century image of social life which grounds today's crude and arid individualism, though there are currently signs that we are beginning to move away from it. A more realistic view of the earth can give us a more realistic view of ourselves as its inhabitants.