The assumption is a distillation of past experience. When that assumption is applied to a
specific conjecture, the assumption tests the conjecture just as if an experiment had been run. When a conjecture is tested against an assumption, the outcome of that test is signified by one of four reactions: that's interesting (assumption of moderate strength is disconfirmed), that's absurd (strong assumption is disconfirmed), that's irrelevant (no assumption is activated), and that's obvious (a strong assumption is confirmed). Those four reactions are the equivalent of significance tests, and they serve as substitutes for validity. The judgment that's interesting selects a conjecture for retention and further use. That judgment is neither capricious nor
arbitrary because it is made relative to a standard that incorporates the results of earlier tests. That standard takes the form of an assumption, and the conjecture is compared with this standard during theorizing.