Contemporary physics, especially quantum theory, has raised profound questions about the relationship between the methods of science and the reality these methods seek to investigate. D'Espagnat investigates these questions as well as how we should answer them. Part I examines the practices of contemporary physicists and addresses the criticism philosophers of science have made of these practices. The doctrine of physical realism, adopted by most physicists and many philosophers of science, comprises Part II. Part III explores the consequences of physical realism for our understanding of what science can seek to know of reality, and concludes by outlining the position contemporary physics indicates we should take.