Traditionally it has been thought that scientific controversies can always be resolved on the basis of empirical data. Recently, however, social constructionists have claimed that the outcome of scientific debates is strongly influenced by non-evidential factors such as the rhetorical prowess and professional clout of the participants. This volume of previously unpublished essays by well-known philosophers of science presents historical studies and philosophical analyses that undermine the plausibility of an extreme social constructionist perspective while also indicating the need for a richer and more realistic account of scientific rationality.