This book reveals that scientific logic is an extension of common, everyday logic and that it can and should be understood by everyone. Written by a practicing and successful scientist, it explores why questions arise in science and looks at how questions are tackled, what constitutes a valid answer, and why. The author does not bog the reader down in technical details or lists of facts to memorize. Instead, he places the questions in their historical and cultural context, ranging from the earliest intimations that the earth had a long history to current controversies, even describing the origins, challenges, and promises of modern molecular biology. He uses accessible examples, illustrations, and descriptions to address issues as complex as radiocarbon dating and how we know that DNA is a double helix. The book should prove enlightening to anyone who has been perplexed by the meaning, relevance, and moral or political implications of science.