How does one distinguish faith from delusion?

If a belief lacks evidence that can be shared with others, how can one verify its accuracy, given that delusions do occur?Further, since religious experiences can be evoked electrically and by drugs, how can one verify that such an experiences is from an external agency? Here, since all people share a common biochemistry, even common experience is no indication of accuracy.If a belief cannot be tested, how can one justify going farther than not knowing if it is accurate?I do not see that absence of contrary evidence justifies beliefs.