 The label ‘reduction’ has been applied to a certain type of progress in science. As this process has been the subject of much philosophical controversy, it is the task of the philosophers of science to give a rational reconstruction of the essential features of reduction. […] Scientific progress may broadly be divided into two types: (1) an increase in factual knowledge, by the addition to the total amount of scientific observations; (2) an improvement in the body of theories, which is designed to explain the known facts and to predict the outcome of future observations. An especially important case of the second type is the replacement of an accepted theory (or body of theories) by a new theory (or body of theories) which is in some sense superior to it. Reduction is an improvement in this sense. (Kemeny &amp; Oppenheim 1956: 6f.)