Maybe there is a spirit of love and justice that lures and inspires and strengthens and sustains us. I like to think so. I'll probably never know. But I can allow the vision to change the way I live. That's what Jack Miles is talking about when he talks about pious agnosticism.
Pious agnosticism means acting as if.
That may not sound legitimate to some of us, who have struggled to reach the point where we are not asking ourselves to mouth words we don't believe. But acing as if is different from pretending to believe. It's more like playing with metaphor. And it's not an uncommon idea in religious circles. It appears in pagan practice, where literal belief is not always required for the circle to be cast and magik to be created.