This book, written for a wide readership with some background in the natural sciences, addresses the very old problem of the mind-brain-relationship. The authors, all well-known scientists, approach the subject in different stages. The first part addresses some general principles based on physics, computer science, and theoretical biology. The two following parts deal with the problem at different organizational levels, from the microscopic to the macroscopic. The fourth part addresses the subjective level founded on the findings of psychologists and neurophysiologists.