This is the second volume in a series that records the official Symposium Pro- ceedings of the Jean Piaget Society. Like the first volume, this work includes theoretical, empirical, and applied aspects of Jean Piaget' s seminal epistemology. The focus of this publication is the intricate interplay of language development and the development of operational thought. All the papers in this volume were presented at the third and fourth annual symposia of the Society. The authors are a formidable group of scholars from around the world who are working in Piagetian theory in many fields of endea- vor. Their work shows the breadth and depth of Piaget's studies, as well as the richness of his ideas over time. The Jean Piaget Society was founded to provide a forum in which scholars and educators could examine and explicate the concepts of genetic epistemology. In many cases, the papers presented at the annual symposia raise many more issues than they resolve. That they generate discussion and further research is self-evident. Such activity is a tribute both to Professor Piaget and to the Society. Further volumes in this series will record the research presented at later symposia.