Ex nihilo nihil fit. For this book I owe much to James Allen, James Blandford, A. J. Campbell, Kelly Fisher, Marilyn Goldman, Judith Haynes, Richard R. Hobbs, R. P. Lucas, Robert Kerrigan, Llewellyn Williams, George Witte, Andrew T. Young, George Zabounian, and many others who gave of their time to contribute or criticize. All errors and deficiencies are my own.