Deficiency arguments against empiricism and the question of empirical indefeasibility

I give a brief overview of Albert Casullo’s Essays on A Priori Knowledge and Justification (2012), followed by a summary of his diagnostic framework for evaluating accounts of a priori knowledge and a priori justification. I then discuss Casullo’s strategy for countering deficiency arguments against empiricism. A deficiency argument against empiricism can be countered by mounting a parallel argument against moderate rationalism that shows moderate rationalism to be defective in a similar way. I argue that a particular deficiency argument put forth by George Bealer in “The Incoherence of Empiricism” (1992) can withstand a parallel challenge mounted by Casullo (2012, Ch.6).