*Department of Economics and of History, University of Iowa. Eleanor Birch, Thomas Borcherding, Ross Eckert, Anthony English, Clifford Geertz, Albert Hirschman, Linda Kerber, Charles Kindleberger, Meir Kohn, David Landes, much of the McCloskey family (Laura, Helen, and Joanne), Joel Mokyr, Erin Newton, much of the Solow family (John, Barbara, and Robert), Richard Sutch, Donald Sutherland, Steven Webb, A. Wick, and Barbara Yerkes have favored me with comments. The paper originated a long time ago in a course for graduate students at the University of Chicago. I thank the students for their help. As usual, Marguerite Knoedel has been patient with my excessive number of drafts. The John Simon Guggenheim Foundation, the National Endowment for the Humanities, the Institute for Advanced Study, and the University of Iowa provided the financial security to write them.