In this classic of modern scientific literature, Sir Charles Sherrington describes the physical basis of life with particular emphasis on human consciousness and its origins in living substance. The author proposes the fundamental questions of man's physical nature: What is life? Where in nature did it originate? What are its limits? How did mind evolve from it? And where, in nature, does consciousness reside? The book centres on the writings of the little-known sixteenth-century physician Jean Fernel. After setting out Fernel's views on the nature of man, Sherrington proceeds to develop his own thoughts, drawing upon a wide variety of philosophical theories. Using Fernel as a historical case study, the book demonstrates how any scientific outlook is always part of its age, and shows how views on the eternal enigmas of mankind, mind and life have changed radically over time. Sherrington's book is important in the history of ideas for its assessment of the value of advances in natural science as a framework for the development of natural theology.