Many traditional books on the history of medicine focus on those key persons, dates, and events that led to the current theories of modern medicine. In his foreword to A History of Immunology, Arthur Silverstein outlines 3 principles that might help the medical historian more accurately describe how medical theories develop. First, medical historians should avoid the trap of viewing history through the lens of current paradigms or interpreting past events in current context. Second, mistaken interpretations, blind alleys, and premature discoveries are as much a part of medical history as the well-known discoveries that support the current paradigm. Third, extrascientific forces can dramatically influence the course of scientific discovery and development. Religion, war, and politics have all influenced the development of immunology. With these principles in mind, Silverstein chronicles the conceptual development of immunology, including the stories of scientists both luminary and obscure. This book is an intellectual history of immunology, including both the quantum leaps and the dead-end theories.