Abstract

On a rational model of science (cf. Lakatos or Laudan), to decide on the appropriate type of explanation of a given scientific change requires a normative assessment made by reference to the model. Showing that a transition fits the model, displays it to be rational and thereby explains it. On the strong programme in the sociology of scientific knowledge (cf. Bloor and Barnes), normative assessment is irrelevant to explanation. All changes require the same type of explanation (the symmetry thesis); namely, a sociological one. The symmetry thesis is false. Scientific change can be explained rationally but without extensive normative assessment using the minimal rationality model (minirät). However, explaining scientific progress as opposed to mere change, requires a maximal rationality model (maxirat) which involves normative assessment.