Metaphysical Pseudo-underdetermination

At the heart of the realist epistemology of science lies the belief that empirically successful theories deliver truth. This belief is challenged by the underdetermination of theory by evidence, which arises when rival theories that are contradictory in their unobservable constituents entail observationally indistinguishable consequences. Hence, the scientific realist is elicited to withdraw their ontological commitment to the unobservable aspects of reality. Earlier counterarguments aiming at weakening the thesis of underdetermination have been largely formulated in conceptual and extra-empirical terms. In this essay, I showcase the strength of a pragmatic route to dispel certain occurrences of empirical underdetermination. To that end, I critically examine an intriguing argument, originally advanced by William Newton-Smith, seeking to underdetermine Newton’s theory in classical mechanics by constructing a rival theory termed Notwen’s theory. Notwen’s theory mirrors the core relationships of the parent theory but operates on discrete, instead of continuous, time and space. Newton’s theory and Notwen’s theory are posited to be empirically equivalent yet ontologically divergent. Here, I argue that the competition between Newton’s theory and Notwen’s theory does not constitute a genuine case of empirical underdetermination. Instead, I denote this occurrence as pseudo-underdetermination, as the empirical evidence necessary to resolve the tie between competing theories has consistently been available. First, I dissolve the empirical equivalence by providing a set of counterfactual scenarios that leverage the differentiation constraint inherent to Newton’s theory but lacking in Notwen’s theory. Second, I show that the ontological commitment of the sophisticated scientific realist is resilient to these rival theories owing to the parasitic nature of Notwen’s theory. Overall, this analysis underscores the effectiveness of an operative approach in resolving instances of empirical underdetermination emerging from ad hoc-generated rival theories.