The four papers and the comment that make up the bulk of this issue of Perspectives on Science, originated in a session organized by Friedrich Steinle for a meeting of the History of Science Society in Denver in 2001. We were struck by the extent to which, in spite of their differences, each of the papers managed to surmount some of the obstacles that beset the delicate, and sometimes difacult, relationship between history of science and philosophy of science. The authors have reworked their papers to highlight the intimate interactions in their work between detailed history of science and some core issue(s) in philosophy of science. The papers deal with different historical episodes and the authors speak from distinctively divergent viewpoints, but each of them develops speciac ways of intertwining historical and philosophical work in ways that improve both the historical studies and the philosophical analysis. This is an accomplishment of no small importance. Attempts to bring historical and philosophical studies of science into close contact with one another have a relatively long history. During an important formative period for the philosophy of science in the nineteenth century, many authors, perhaps most notably William Whewell, sought to base general accounts of science on serious studies of its history (see The Philosophy of the Inductive Sciences, Founded upon their History, 1840). Although the history and the philosophy of science have often proceeded in considerable independence of one another, ever since Whewell’s groundbreaking work there have been notable attempts to provide a historical footing for general philosophies of science. One need only think of Duhem or Mach or, since the 1960s, Hacking, Kuhn, Lakatos, Latour, and Laudan—and many more. Recently, however, mainstream history of science and mainstream philosophy of science have gone in different directions. History of science