According to Alvin Plantinga, it has been widely held since the Enlightenment that if theistic beliefs are to be considered rational, they must be based on propositional evidence. It is not enough for the theist just to refute objections. The theist "must also have something like an argument for [such a] belief, or some positive reason to think that the belief is true." But this is incorrect, Plantinga argues. Basic beliefs are beliefs not based on propositional evidence; such beliefs are "properly basic in a set of circumstances" if they can be so affirmed in those circumstances "without either violating an epistemic duty or displaying some kind of noetic defect." And, according to Plantinga, theistic beliefs can be properly basic. For example, he argues that "under widely realized conditions it is perfectly rational, reasonable, intellectually respectable and acceptable to believe there is such a person as God without believing it on the basis of evidence — propositional evidence vs. the kind instanced by 'the evidence of the senses'." But can a properly basic belief such as this have any epistemic credibility (warrant) if it is not conferred by other propositions whose epistemic status is not in question? Yes, Plantinga replies. There are two significantly different ways in which a proposition can acquire warrant. There is propositional warrant — warrant conferred by an evidential line of reasoning from other beliefs. However, there is also nonpropositional warrant.