Abductive Two-Dimensionalism: A New Route to the A Priori Identification of Necessary Truths

Epistemic two-dimensional semantics (E2D), advocated by Chalmers (2006) and Jackson (1998), among others, aims to restore the link between necessity and a priority seemingly broken by Kripke (1972/1980), by showing how armchair access to semantic intensions provides a basis for knowledge of necessary a posteriori truths (among other modal claims). The most compelling objections to E2D are that, for one or other reason, the requisite intensions are not accessible from the armchair (see, e.g., Wilson 1982, Melnyk 2008). As we substantiate here, existing versions of E2D are indeed subject to such access-based objections. But, we moreover argue, the difficulty lies not with E2D but with the typically presupposed conceiving-based epistemology of intensions. Freed from that epistemology, and given the right alternative---one where inference to the best explanation (i.e., abduction) provides the operative guide to intensions---E2D can meet access-based objections, and fulfill its promise of restoring the desirable link between necessity and a priority. This result serves as a central application of Biggs and Wilson 2016 (summarized here), according to which abduction is an a priori mode of inference.