To five wondrous creatures, named in the order of their appearance on this planet: Aaron Victoria Benton Jonathan And Meredith Acknowledgments This book would not have been possible without the support, and especially the patience, of David Harris, John Betancourt, Byron Preiss, Susan Allison, Ginjer Buchanan, and Peter Heck. There was many a slip between cup and the lip, but thanks to their collective efforts, never a drop of the good stuff was lost. The book stands as proof once again that every writer needs at least one editor, and sometimes five or six is no bad idea. Thanks are also due to Thomas B. Allen and Eleanore Fox, neither of whom had time to read the manuscript, and both of whom did. I. A Robot May Not Injure a Human Being, or, Through Inaction, Allow a Human Being to Come to Harm. II. A Robot Must Obey the Orders Given It by Human Beings Except where Such Orders Would Conflict with the First Law. III. A Robot Must Protect Its Own Existence As Long As Such Protection Does Not Conflict with the First or Second Law. ...THE Spacer-Settler struggle was at its beginning, and at its end, an ideological contest. Indeed, to take a page from primitive studies, it might more accurately be termed a theological battle, for both sides clung to their positions more out of faith, fear, and tradition than through any carefully reasoned