With the publication of J.L. Schellenberg’s Divine Hiddeness and Human Reason, in recent years philosophers of religion have focused their attention on the problem of the “hiddenness of God”, the evident fact that, if God exists, he is not as overtly obvious as he could be. The psalmists and prophets often lamented this apparent absence of God. And Bertrand Russell, imagining a possible meeting with God in the afterlife, famously said he would explain his atheism by the lack of sufficient evidence. A good place to start exploring the problem is in a recent collection of essays: Divine Hiddenness: New Essays. On a more pedestrian level, Phillip Yancey has wrestled with this question at length in his typically poignant and honest style. See his Disappointment with God and Reaching for the Invisible God.