The Obvious.

Infallibilism about a priori justification is the thesis that for an agent A to be a priori justified in believing p, that which justifies A's belief that p must guarantee the truth of p. No analogous thesis is thought to obtain for empirically justified beliefs. The aim of this article is to argue that infallibilism about the a priori is an untenable philosophical position and to provide theoretical understanding why we not only can be, but rather must be, a priori justified in believing some false propositions. The argument develops notions of obviousness and conceptual understanding as a means of affording insight into the conditions for having a priori justification and, consequently, into why infallibilism cannot stand.