This book presents ideas developed by Paul Cobb and his colleagues that have significantly influenced the field of mathematics education over the past three decades. In this volume, they are brought together for readers to present a clear view of how the field has changed during that time. During his career Cobb moved from looking at a single child's mathematical reasoning, to a class learning a particular mathematical topic, to a group of school teachers, and to a school district with all its teachers, teachers' teachers and principals. It was his wish to make a real difference and his constantly revised understanding of what it takes to do so that dictated this gradual broadening of the unit of analysis. This development is presented in this book with the help of chronologically organized previously published papers, each of which represents a distinct stage in this intellectual journey and is preceded by a new commentary that sheds additional light on the processes of reconceptualization and thus helps the reader to understand the reasons, mechanisms, and outcomes of researchers' constant pursuit of new insights. This book thus demonstrates how research develops and evolves when theory and practice are taken as mutually informing aspects of the researcher's work. In this sense, the volume is relevant to audiences primarily interested in practical aspects of mathematics education as well as to those whose primary interests lie in theoretical developments.

List of contributors
Acknowledgments
Foreword
James Greeno
Introduction
Koeno Gravemeijer and Erna Yackel
1. Radical Constructivism
Introduction
The constructivist researcher as teacher and model builder
Paul Cobb and Leslie P. Steffe
Journal for Research in Mathematics Education, 14 (1983), 83-94.
2. Social Constructivism
Introduction, written with Erna Yackel
Young children's emotional acts while doing mathematical problem solving
Paul Cobb, Erna Yackel, and Terry Wood
In D. McLeod & V. A. Adams (Eds.) (1989), Affect and mathematical problem solving: A new perspective, (pp. 117-148). New York: Springer-Verlag.
3. Symbolizing and Instructional Design - Developing Instructional Sequences to Support Students' Mathematical Learning
Introduction, written with Koeno Gravemeijer and Erna Yackel
Learning from distributed theories of intelligence
Paul Cobb
Mind, Culture, and Activity, 5(1998), 187-204.
4. Classroom Mathematical Practices
Introduction, written with Michelle Stephan and Janet Bowers
Participating in classroom mathematical practices
Paul Cobb, Michelle Stephan, Kay McCain, Koeno Gravemeijer
The Journal of Learning Sciences, 10(1&2) (2001), 113-163.
5. Diversity and Equity
Introduction, written with Lynn Liao Hodge and Melissa Gresalfi
Culture, identity, and equity in the mathematics classroom
Paul Cobb and Lynn Liao Hodge
Expanded version of a chapter with the same title in N. S. Nasir and P. Cobb (Eds.) (2007). Improving access to mathematics: Diversity and equity in the classroom, (pp. 159-171). New York: Teachers College Press.
6. The Institutional Setting of Mathematics Teaching and Learning
Introduction, written with Chrystal Dean, Teruni Lamberg, Jana Visnovska, and Qing Zhao
The collective mediation of a high stakes accountability program: Communities and networks of practice
Paul Cobb and Kay McClain
Mind, Culture, and Activity, 13 (2006), 80-100.
Epilogue
Anna Sfard