 What happens in such cases? Understanding alone does not seem to justify you in believing. To be justified in believing the proposition—in a way that does not depend upon testimony—you need to “see” it for yourself. Such “seeing” has various names, e.g., “intuition”, “rational insight”, “clear and distinct perception”. But whatever it is called, it is hard to deny it is an experience. So the standard view faces a problem: there is a distinctive kind of experience apparently required for a priori justification in believing, and hence, a priori knowledge of, some propositions typically regarded as a priori and perhaps even self-evident. One might be led to question whether one who understands such a proposition but has not yet had the experience of “seeing” the proposition to be true even has propositional justification. Finally, one might be led to wonder whether this kind of “experience” is always required for a priori knowledge and justification that does not depend upon proof.