 (9) Kuhn’s novel constructive move in dealing with the rationality of paradigm change was to bring in a prospective dimension of heuristic fertility judgments. From the point of view of key, creative scientists, the old paradigm has exhausted its resources, whereas radical new ideas and practices can not only resolve some old anomalies (retrospective confirmation) but, equally importantly, can reinvent and thereby preserve the field by opening up new frontiers with much interesting new work to be done. For them the field now had a future. To be sure, heuristic guidance was also a feature of normal science, but there it was built in implicitly.