 Lined up in opposition to the various motivations for realism presented in  section 2  are a number of important antirealist arguments, all of which have pressed realists either to attempt their refutation, or to modify their realism accordingly. One of these challenges, the underdetermination of theory by data, has a storied history in twentieth century philosophy more generally, and is often traced to the work of Duhem ([1906] 1954: ch. 6; this is not an argument for underdetermination as such, but is regarded as sowing the seeds). In remarks concerning the confirmation of scientific hypotheses (in physics, which he contrasted with chemistry and physiology), Duhem noted that a hypothesis cannot be used to derive testable predictions in isolation. To derive predictions one also requires “auxiliary” assumptions, such as background theories, hypotheses about instruments and measurements, etc. If subsequent observation and experiment produces data that conflict with those predicted, one might think that this reflects badly on the hypothesis under test, but Duhem pointed out that given all of the assumptions required to derive predictions, it is no simple matter to identify where the error lies. Different amendments to one’s overall set of beliefs regarding hypotheses and theories will be consistent with the data. A similar result is commonly associated with the later “confirmational holism” of Quine (1953), according to which experience (including, of course, that associated with scientific testing) does not confirm or disconfirm individual beliefs per se, but rather the set of one’s beliefs taken as a whole. This sort of contention is now commonly referred to as the “Duhem-Quine thesis” (Quine 1975; see Ben-Menahem 2006 for a historical introduction).