This is an introductory survey to the philosophy of science suitable for beginners and nonspecialists. Its point of departure is the question: why should we believe what science tells us about the world? In this attempt to justify the claims of science the book treats such topics as observation data, confirmation of theories, and the explanation of phenomena. The writing is clear and concrete with detailed examples drawn from contemporary science: solar neutrinos, the gravitational bending of light, and the creation/evolution debate, for example. What emerges is a view of science in which observation relies on theory to give it meaning and credibility, while theory relies on observation for its motivation and validation.