Traditional rationalist approaches to a priori epistemology have long been looked upon with suspicion for positing a faculty of rational intuition capable of knowing truths about the world apart from experience. Conceptualists have tried to fill this void with something more empirically tractable, arguing that we know a priori truths due to our understanding of concepts. All of this theorizing, however, has carried on while neglecting an entire cross section of such truths, the grounding claims that we know a priori. (...) Taking a priori grounding into account poses a significant challenge to conceptualist accounts of a priori knowledge, as it is unclear how merely understanding conceptual connections can account for knowledge of grounding. The fact that we do know some grounding truths a priori, then, is a significant mark in traditional rationalism’s favor, and the next frontier for those who aim to eliminate the mystery surrounding a priori knowledge. (shrink)