Current research into the psychology of children's mathematics is extremely diverse. The present volume reflects this diversity; it is unique in its breadth, bringing together accounts of cutting-edge research from widely differing, sometimes opposing viewpoints. The reader with a grounding in developmental psychology but no knowledge of mathematical development will enjoy a wide ranging and challenging summary of current trends. Those already familiar with some of the work may take the opportunity to broaden their knowledge and to evaluate new methodologies and the insights they offer. The book is an invitation to explore a complex set of phenomena for which no unitary explanation can be offered. It aims to show that apparently disparate research perspectives may be complementary to each other; and to suggest that progress towards a comprehensive account of mathematical skills may require a broad-based understanding of research from more than one viewpoint.