On what basis does the theist believe in the truth of his or her religion? Some theists argue that faith is both necessary and sufficient to demonstrate the truth of his or her religious beliefs. Others, while perhaps believing in the sufficiency of faith, argue that it is lawful and to be encouraged to offer concrete evidence for the truth of one’s religious beliefs, so that one’s beliefs are not a “leap in the dark.” Evidentialism, as the name implies, is the notion that we ought to weigh beliefs as proportioned by the evidence for them(Forrest, 2011).
An example that Forrest uses is a weather forecaster noting that for over 200 years of recording weather, an unusually wet winter anticipates in 85% of cases an unusually hot summer, and determining that, since this winter is unusually wet, our summer will most likely be unusually hot(Forrest, 2011). The evidentialist who advocates such an epistemology would reason that if we have comparable evidential support for this or that religious belief, we are justified (or perhaps even obligated) to accept it as true, and if we do not have such evidence, we are not justified in accepting it(or perhaps even obligated to reject its truth claims).
Forrest, Peter, “The Epistemology of Religion”, The Stanford Encyclopedia of Philosophy (Winter 2011 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/win2011/entries/religion-epistemology/>.