It has become commonplace to draw parallels between the rapid growth of digital communications systems and the introduction of the printing press over five hundred years ago. George Landow' s claim (or is it a warning?) that "electronic text processing marks the next major shift in information technology after the development of the printed book" takes its cue from Marshall McLuhan' s provocative comments a generation ago. As that Canadian communications theorist observed, media are not transparent windows-- by their very function of mediation, they have power to reshape reality. The view of the world that the print medium conveys is likely to be quite distinct from the view made possible by electronic media, not just in content but also in structure.