 The Navigation Question: Granted  (WMR),  we might still wonder about knowledge of secondary possibility. Is there any a priori way of inferring secondary possibility from primary possibility? Simply put: can we navigate a priori from primary to secondary possibility? Chalmers thinks that in some special cases we can. Such cases require that an expression’s primary and secondary intensions coincide. Candidate examples include, most notably, the class of phenomenal truths as well as mathematical and analytic truths (Chalmers 2010: ch. 6). However, that raises a worry that on Chalmers’ conceivability theory we won’t be able to have a priori access to most of the modal metaphysical realm. Conceivability seems a limited resource for knowledge of metaphysical modality.