How then does this give rise to underdetermination, a presumptive concern for realism? The argument from underdetermination proceeds as follows: let us call the relevant, overall sets of scientific beliefs “theories”; different, conflicting theories are consistent with the data; the data exhaust the evidence for belief; therefore, there is no evidential reason to believe one of these theories as opposed to another. Given that the theories differ precisely in what they say about the unobservable