ROGER PENROSE is a mathematical physicist; Rouse Ball Professor of Mathematics at the University of Oxford; and author of Techniques of Differential Topology in Relativity; Spinors and Space-time, (with W. Rindler, 2 vols.); The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics; Shadows of the Mind: A Search for the Missing Science of Consciousness; The Nature of Space and Time (with Stephen Hawking). He is also coeditor of Quantum Gravity 2: A Second Oxford Symposium (with C.J. Isham and Dennis W. Sciama); and Quantum Concepts in Space and Time (with C.J. Isham).