There's an abyss at the edge of the metaphysical and modal proofs, a screaming darkness made of terror no rational argument can penetrate. The only way through is Kierkegaard's leap, to go directly into what Camus called "spiritual suicide," to hurl yourself headlong into nothingness with the sincere belief that there is Someone in there that will not only catch you, but show you that the emptiness is a lie, a falsehood and privation of a far more glorious reality than you could have fathomed on the dark side of oblivion.
Other times, though, I think belief of whatever kind must be the most basic wisdom imaginable, requiring no great insight nor any particular effort. We yearn for what we need, and find what we seek, from the moment we begin to encounter the world. It is one of the most immediate experiences of being human; to reach out, and find someone reaching back.