cassidy has performed a biographical tour de force. he beautifully explicates heisenberg's physics in all its ramifications, provides insightful portraits of heisenberg's contemporaries and their roles in his life and work and at the same time unsentimentally analyzes heisenberg the man. cassidy gies us heisenberg the genius and heisenberg the nazi collaborator. yet his understanding of german culture and history is such that one comes away feeling entirely reeducated with respect to these cataclysmic events. his writing is lucid and vivid. my only criticisms are the lack of mathematical formulations- somemtimes only the math can convey the principle- and his occasional failure to define more abstuse mathematical terms. overall this is a magnificent work.