GAIA, named after the ancient Greek mother-goddess, is the notion that the Earth and the life on it form an active, self-maintaining whole. By its use of personification it attacks the view that the physical world is inert and lifeless. It has a scientific side, as shown by the new university departments of earth science which bring biology and geology together to study the continuity of the cycle. It also has a visionary or spiritual aspect. What the contributors to this book believe is needed is to bring these two angles together. With global warming now an accepted fact, the lessons of GAIA have never been more relevant and urgent.