This discussion note aims to show that Moti Mizrahi does not make clear whether the proponents of the semantic view of scientific progress reject or accept the inference rule of Addition. If they reject the rule, then it does not make sense that Mizrahi contrives different types of disjuncts ‘on behalf of’ proponents of the semantic view. If they accept the rule, then the characterisation of the semantic view that Mizrahi discusses has nothing to do with the supposedly arbitrariness of (...) scientific progress, as Mizrahi contends. (shrink)