Part of a series in Studies in Rhetoric and Communication, this book casts a fresh light on the process by which claims are validated. If scientists cannot justify their claims in positivistic terms, how can a claim be legitimatized? This book looks at the special problems and values governing the communicative practices of scientists. The author demonstrates that when scientists address their claims to other scientists, they create a special kind of rhetoric with rules that distinguish scientific discourse from other discourse and allow claims to be judged as scientific or not. The author moves beyond the general idea that science has rhetorical dimensions to outline in detail an informal rhetorical logic that constrains discourse. In particular, the book looks at how arguments are designed and on the grounds on which they persuade and are evaluated as peculiarly scientific claims.