There is no doubt that ?the gene?played a tremendous role in the history of the twentieth century life sciences. Yet Staffan Mler-Wille and Hans-J顤g Rheinberger argue that there never was a universally accepted, stable definition of the gene. In this remarkable history, they not only show that the concept of the gene was in continual flux but also argue that this is a typical feature of historically influential and productive scientific concepts. In their view, the gene concept owed its position as a central organizing theme not to its rigorous definition but, rather, to the fact that it was progressively opened to instrumental manipulation. Highly relevant to contemporary thinking in genetics and genomics, this book will speak volumes to biologists, historians, and philosophers.