 Many analysts have played with possible relationships between the sciences’ assumed rationality and assumed progressiveness. The central issue for them is analogous to the question in Rodgers and Hammerstein’s Cinderella: Is science progressive because it’s rational, or is it rational because it’s progressive? (Kuhn [1962] 1970a: 162, had asked: Does a field make progress because it is a science, or is it a science because it makes progress?”) The underlying question is whether rationality is basic and fundamental rather than derivative to something else. Those like Laudan who make it derivative need to defend their position against the objection that they are committing a verificationist fallacy of confusing rationality itself (its constitutive nature) with the criteria for applying the term ‘rational’. Are momentary success or longer-term progress constitutive of rationality or merely consequential indicators of it (or neither)?