Book excerpt: In these thought-provoking, witty essays, some of America's most distinguished geographers explore ten geographic ideas that have literally changed the world and the way we think and act. They tackle ideas that impose shape on the world, ideas that mold our understanding of the natural environment, and ideas that establish relationships between people and places. The contributors, who include several past presidents of the Association of American Geographers, members of the National Academy of Sciences, and authors of major works in the discipline, are: Elizabeth K. Burns, Patricia Gober, Anne Godlewska, Michael F. Goodchild, Susan Hanson, Robert W. Kates, John R. Mather, William B. Meyer, Mark Monmonier, Edward Relph, Edward J. Taaffe, and B. L. Turner, II.