As dissatisfaction with the current status of school mathematics grows worldwide, educators and professionals alike are calling for reforms and instructional changes. Yet, significant changes can only be achieved if each educator of school mathematics personally rethinks various aspects of mathematics instruction, and identifies concrete ways in which their current practice could be modified. Before such visions can be meaningfully implemented in classrooms, it is important that mathematics teachers and educators examine critically both the assumptions and implications of the vision for school mathematics that the reports propose. This book is intended to support educators in such a challenging enterprise by focusing attention on "errors" and their use in mathematics instruction. Throughout the book, an approach to errors as opportunities for learning and inquiry will be developed and employed both as a means to create the kinds of instructional experiences advocated for school mathematics reform, and as a heuristic to invite reflections about school mathematics as well as mathematics as a discipline. REVIEWS: "...Raffaella Borasi's newest book offers important contributions to the current debate on school mathematics reform." - Journal for Research in Mathematics Education "There are some great bits of philosophy in this book..." - Mathematics Teaching