The papers in this volume address an incredibly basic question in stone tool studies, namely whether a particular lithic artifact should be classified as a tool, thus implying that at some time in the past it was used directly to perform activities, or whether it should instead be classified as a core, meaning that its purpose was to produce flakes some of which were then made into tools. This question is so basic that it would seem archaeologists should have solved it by now, and in most instances this is the case. This volume, however, looks at some of the remaining problem cases in part to find out if they can be solved, but mainly because the really difficult cases raise the more challenging and interesting methodological issues, which can in turn lead us to question and overhaul long-held assumptions and long-used approaches to the study of stone tools. This is, in fact, what happens in this volume with papers that discuss assemblages from Lower/Middle Paleolithic sites in Europe and southwest Asia to more recent Holocene sites in the New World and Australia. In some instances the very idea of classifying these artifacts as one or the other is entirely discarded; in other instances, it is assumed they fit in both categories, and the behavioral implications are assessed. The end result in each case is a richer understanding of the past less encumbered by categories archaeologists bring to the study.