Hutton, James (1726-1797), a Scottish philosopher and chemist, was a pioneer in the field of geology. His main contributions included the ideas that Earth was immensely old and that its features were constantly and gradually changing. He argued that many such changes were caused by heat within Earth. Hutton discussed this geological change in his book Theory of the Earth (1795). His theory that geological forces are the same now as in the past became known as uniformitarianism.