Until recently, realists and anti-realists alike have assumed that any approximations which appear in explanations and confirmations in the mathematically oriented physical and biological sciences are “mere distractions” (Laymon 1989, p. 353). When approximation techniques must be used, they are typically justified by appeals to their numerical accuracy. However, recent interest in computational complexity in the sciences has revealed that numerical accuracy is not always the only criterion which should be invoked to justify the use of approximations. Cartwright (1983), Franklin (...) (1988) and others have suggested that causal accuracy should be added as a criterion.Numerical and causal accuracy are important. However, they form a sufficient set of justificational criteria only when certain—often unstated—conditions obtain. These conditions are actually assumptions which are often not satisfied, especially in the computationally complex situations which characterize discovery and exploratory contexts. In these contexts, we need to concentrate on “delineating a justificatory set which is relevant to [the] given epistemic situation” (Duran 1988, p. 273). (shrink)