For centuries, observers have noted the many obstacles to intellectual change in science. In a much-discussed paper published in Scientific American in 1972, molecular biologist Gunther Stent proposed an explicit criterion for one kind of obstacle to scientific discovery. He denoted a claim or hypothesis as "premature" if its implications cannot be connected to canonical knowledge by a simple series of logical steps. Further, Stent suggested that it was appropriate for the scientific community to ignore such hypotheses so that it would not be overwhelmed by vast numbers of false leads. In this volume, eminent scientists, physicians, historians, social scientists, and philosophers respond to Stent''s thesis.