This book collects the first section of Gifford Lectures delivered by the distinguished neuroscientist, Sir John C. Eccles, at the University of Edinburgh 1977–78. This opening series was later followed by a collection entitled The Human Psyche, which builds upon the final three lectures given here. Beginning with a reference to Sherrington’s noted lectures given forty years earlier, Eccles argues that, given the advances made in terms of knowledge, problems have to be revisited.