What is the significance of mankind in the Universe? Ever since Copernicus, scientists have been moving man further and further from his lofty position at the center of Creation. But in recent years a startling new concept has evolved that puts humans more firmly than ever in a special position. Known as the Anthropic Cosmological Principle, it holds that the fundamental structure of the Universe is determined by the existence of intelligent observers: the universe is as it is because if it were otherwise, observers could not exist. In its most radical version, the Anthropic Principle asserts: "Intelligent information-processing must come into existence in the Universe, and once it comes into existence, it will never die out." More than a revolutionary theoretical concept, the anthropic principle can be used as a powerful predictive tool leading to a fundamental change in the way we understand physical phenomena. This groundbreaking work explores the many ramifications of the principle and covers the whole spectrum of human inquiry from Aristotle to Z bosons. Chapters cover the definition and nature of life, the search for extraterrestrial intelligence, and the interpretation of the quantum theory in relation to the existence of observers. The book will be of vital interest to philosophers, theologians, mathematicians, scientists, and historians--and to anyone who ever wondered if there was any connection between the vastness of the universe of stars and galaxies and the existence of life within it on a small planet out in the suburbs of the Milky Way. About the Authors: John D. Barrow is University Lecturer in Astronomy at the University of Sussex, England. Frank J. Tipler is Associate Professor of Mathematical Physics at Tulane University.