There is a great need for a new approach, new methods and new tools in teaching, man's oldest and most reactionary craft. There is great need for a rapid increase in the productivity of learning. There is, above all, great need for methods that will make the teacher effective and multiply his or her efforts and competence. Teaching is, in fact, the only traditional craft in which we have not yet fashioned the tools that make an ordinary person capable of superior performance. In this respect, teaching is far behind medicine, where the tools first became available a century or more ago.