underdetermine

1967 A. H. Armstrong (ed) The Cambridge History of Later Greek and Early Medieval Philosophy He recognised that, in constructing his laws, the physicist must go beyond the ‘facts’ which inevitably underdetermine his theories. Boltzmann rightly accused both the idealists and the inductivists of having ignored this basic limitation on the certainty of all scientific hypotheses.

1: All the available evidence of a certain type underdetermines which of several rival conclusions is correct. 2: Only evidence of that type is relevant to believing one of these conclusions. 3: Therefore, there is no evidence for believing one among the rival conclusions. The first premise makes the claim that a theory is underdetermined. The second says that rational decision (i.e. using available evidence) depends upon insufficient evidence.