Wittgenstein’s On Certainty does not provide a comprehensive examination of religious belief. But in many of the aphorisms we can find clues that are helpful in discussing and understanding religious phenomena. His analysis of the concepts of knowing, believing, doubt, certainty, and acting provides valuable input for a discussion of religious belief.
Not being a religious believer himself, but being inspired (and sometimes tortured) by high ethical demands on himself makes him a trustworthy philosophical authority to speak about the relation between religion and epistemology.
In my opinion, Wittgenstein’s concept of hinge beliefs plausibly explains why religious conviction about the most amazing religious dogmas can be as strong as we often find it in a true believer. At the same time it puts into perspective the alleged scientific foundation of the supporter of a scientific world-picture. In fact, both camps rely on a large number of unconsciously acquired hinge beliefs that determine their acting. Acting with sureness feels like if it were based on knowledge, but in effect it is often rather based on a mental state of conviction, that is on nonepistemic certainty. At the basis of this certainty are hinge beliefs, which can have their roots in religious, scientific, or everyday life. The subsets of beliefs can overlap, providing the religious believer with enough foundation for leading her everyday life in a scientifically organized environment and allowing the scientific believer enough room for shaping her live in accordance with her values and spiritual inclinations.
Wittgenstein compares religious belief to a passion and this makes even better understandable the function it has in the life of a believer, regardless of her attitude towards science, philosophy, or epistemology.