An eminent pioneer of modern protein chemistry looks back on six decades in biochemical research and education to advance stimulating thoughts about science--how it is practiced, how it is explained, and how its history is written. Taking the title of his book from Robert Boyle's classic, The Sceptical Chymist (1661), and Joseph Needham's The Sceptical Biologist (1929), Joseph Fruton brings his own skeptical vision to bear on how chemistry and biology interact to describe living systems. Scientists, philosophers, historians, and sociologists will seize upon the questions Fruton raises: What is the nature of the tension between the chemical and the biological sciences? What are the roots and future direction of molecular biology? What is the proper place of expert scientists in the historiography of science? How does the "scientific method" really work in practice? These and many other topics are fair game for this author's wise critiques. In a stimulating final chapter, Fruton analyzes the evolution of key terms and symbols--the conceptual underpinnings--used in the biochemical literature.