 Kuhn’s (1962) strategy was to avoid the notion of truth and to understand science as an activity of making accurate predictions and solving problems or “puzzles”. Paradigm-based normal science is cumulative in terms of the problems solved, and even paradigm-changes or revolutions are progressive in the sense that “a relatively large part” of the problem-solving capacity of the old theory is preserved in the new paradigm. But, as Kuhn argued, it may happen that some problems solved by the old theory are no longer relevant or meaningful for the new theory. These cases are called “Kuhn-losses.” A more systematic account of these ideas is given by Laudan (1977): the problem-solving effectiveness of a theory is defined by the number and importance of solved empirical problems minus the number and importance of the anomalies and conceptual problems that the theory generates. Here the concept of anomaly refers to a problem that a theory fails to solve, but is solved by some of its rivals. For Laudan the solution of a problem by a theory \(T\) means that the “statement of the problem” is deduced from \(T\). A good theory is thus empirically adequate, strong in its empirical content, and—Laudan adds—avoids conceptual problems. 