Quasi-truth and defective knowledge in science: a critical examination

Quasi-truth (a.k.a. pragmatic truth or partial truth) is typically advanced as a framework accounting for incompleteness and uncertainty in the actual practices of science. Also, it is said to be useful for accommodating cases of inconsistency in science without leading to triviality. In this paper, we argue that the given developments do not deliver all that is promised. We examine the most prominent account of quasi-truth available in the literature, advanced by da Costa and collaborators in many places, and argue that it cannot legitimately account for incompleteness in science: we shall claim that it conflates paraconsistency and paracompleteness. It also cannot account for inconsistencies, because no direct contradiction of the form α ∧ ¬α can be quasi-true, according to the framework. Finally, we advance an alternative interpretation of the formalism in terms of dealing with distinct contexts where incompatible information is dealt with. This does not save the original program, but seems to make better sense of the formalism.