PETER F. DRUCKER has been a teacher, writer, and adviser to senior executives for more than fifty years. Author of thirty-one books including his recently released Management Challenges for the 21st Century, he is honorary chairman of the Drucker Foundation and Clarke Professor of Social Sciences at the Claremont Graduate University in Claremont, California. PETER M. SENGE is a senior lecturer at the Massachusetts Institute of Technology and chairman of the Society of Organizational Learning, a global community of corporations, researchers, and consultants dedicated to personal and institutional development. He is the author of The Fifth Discipline and the co-author of The Fifth Discipline Fieldbook. FRANCES HESSELBEIN is chairman of the board of governors of the Drucker Foundation and former chief executive of Girls Scouts of the U.S.A. She is the lead editor of five books, including The Leader of the Future and Leading Beyond the Walls, published by the Drucker Foundation and Jossey-Bass, and is editor-in-chief of the journal Leader to Leader.