 Chalmers still takes PQTI sentences to be a promising candidate for specifying a scrutability base D, but he is open to the possibility that the descriptive vocabulary in PQTI may need to be supplemented in order to capture some truths, such as truths about causal relations or quiddities. But while he can afford to be flexible about the exact nature of the scrutability base, Chalmers’ rationalist program depends on vindicating Apriori Scrutability for any sentence that is evaluable as possibly true or false (169–71). A good deal thus hangs on whether he is right that ideal epistemic procedures allow for apriori justification, given an exhaustive base-level description of a scenario. Chalmers offers arguments to support the plausibility of this view in (2012, ch. 4.).