Gaia is a theory of the Earth that has revolutionised how we see this 'pale blue dot': all living things are part of one great organism and life as a whole shapes the planetary environment. Lovelock and Gaia tells how that came about including the theory's long struggle to gain respectability. Opponents dubbed it mere metaphor or myth, suggested that it was either irrefutable or unnecessary, or argued that it was impossible on Darwinian grounds for life to affect environment on a global scale in any way which could be fruitfully coupled with natural selection. It is not yet clear where it will lead but its impact compares with the greatest of scientific revolutions.