"What lies at the heart of physical inquiry? What are the foundational ideas and working assumptions that inform the enterprise of natural science? What principles guide research? How do scientists decide whether they are building theories in the right direction? Is there a right direction? Do physical theories actually approximate an objective reality, or are they simply useful summaries, mnemonics for experimental results? This book is Nobel Prize winner Jim Peebles's contribution to such big, classic debates in the philosophy of science, drawing on a lifetime of experience as a leading physicist and taking the development of physical cosmology as a 'worked example.' He begins with a consideration of the history of thought about the nature of the physical sciences since Einstein, culminating in a succinct statement of what he sees as the fundamental working assumptions of physics. Then, through a careful examination of the development of the general theory of relativity, Einstein's cosmological principle, the big bang theory, and our current model of the universe, he makes the argument that physical theories ultimately are useful approximations to an objective reality whose nature science is discovering. An essential reflection on and interrogation of the nature and practice of science by a giant in the field, The Whole Truth will be illuminating reading for cosmologists, physicists, and historians, philosophers, and sociologists of science alike"--