This volume treats the development of geological ideas, from antiquity to the present. The significance of ideas about the earth is reflected in the range of thinkers who have written on geological questions: for example, Aristotle and Descartes, with their ideas grounded in philosophy; Werner, with ideas developed as an outgrowth of the German mining tradition; Humboldt, with his effort to produce a holistic picture of nature; Lyell, with his ideas on the earth's age and history; Jeffreys with his geophysics; Lovelock, with his Gaia hypothesis.