In 1963, the University of Chicago Press published a book titled The Structure of Scientific Revolutions, written by Thomas Kuhn, a University of California professor of the history of science. In the book Kuhn hypothesizes about the process by which major changes come about in scientific fields, and conjectures that they probably do not evolve gradually from patient and orderly inquiry by established investigators in the field. Rather, he suggests, revolutions in science come about as the result of breakdowns in intellectual systems, breakdowns that occur when old methods won't solve new problems. He calls the change in theory that underlies this kind of revolution a paradigm shift. I believe we are currently at the point of such a paradigm shift in the teaching of writing, and that it has been brought about by a variety of developments that have taken place in the last 25 years. Briefly, Kuhn's thesis in The Structure of Scientific Revolutions is this. When a scientific field is going through a stable period, most of the practitioners in the discipline hold a common body of beliefs and assumptions; they agree on the problems that need to be solved, the rules that govern research, and on the standards by which performance is to be measured. They share a conceptual model that Kuhn calls a paradigm, and that paradigm governs activity in their profession. Students who enter the discipline prepare for membership in its intellectual community by studying that paradigm. But paradigms are not necessarily immutable. When several people working in a field begin to encounter anomalies or phenomena that cannot be explained by the established model, the paradigm begins to show signs of instability. For a while, those who subscribe to the paradigm try to ignore the contradictions and inconsistencies that they find, or they make improvised, ad hoc changes to cope with immediate crises. Eventually, however, when enough anomalies accumulate to make a substantial number of scientists in the field question whether the traditional paradigm can solve many of the serious problems that face them, a few innovative thinkers will devise a new model. And if enough scientists become convinced that the new paradigm works better than the old one, they will accept it as the new norm.