 It is worth-noting that, methodologically, the divide et impera strategy recommended that the historical challenge to realism can only be met by looking at the actual successes of past successful theories and by showing that those parts of past theories (e.g., the caloric theory of heat or the optical ether theories) that were fuelling theory successes were retained in subsequent theories and those theoretical terms which were central in the relevant past theories were referential. In fact, Vickers has recently made the methodological suggestion that if one’s sole aim is to cope with a historical challenge, then it is sufficient that one shows that the abandoned hypotheses were not essential for the relevant theory’s empirical success, without at the same time taking side on which are the essential theoretical hypotheses. As Vickers claims, in order to respond to a PI-style challenge, “all the realist needs to do is show that the specific assumptions identified by the antirealist do not merit realist commitment. And she can do this without saying anything about how to identify the posits which do merit realist commitment” (2017: 3224). Besides, according to Vickers’s conception of the dialectic of the PI-debate, the onus of proof lies with the antirealist: the antirealist has to reconstruct the derivation of a prediction, identify the assumptions that merit realist commitments and then show that at least one of them is not truthlike by our current lights; and then all the realists need to show is that the specific assumptions were inessential. In sum, Vickers argues that “the project of responding to the historical challenge” and “the project of explaining what realists should commit to” have to be kept distinct (2017: 3222). 