Whether your faith is that there is a God or that there is not a God, if you don’t have any doubts, your are either kidding yourself or asleep. Doubts are the ants in the pants of faith. They keep it awake and moving.
One does not learn anything except by believing something, and — conversely — if one doubts everything one learns nothing. On the other hand, believing everything uncritically is the road to disaster. The faculty of doubt is essential. But as I have argued, rational doubt always rests on faith and not vice versa. The relationship between the two cannot be reversed.
― Lesslie Newbigin,
Proper Confidence: Faith, Doubt, and Certainty in Christian Discipleship
It is not as a child
that I believe in Christ
and profess his teaching;
my hosanna has burst through
a purging flame of doubt.
Mysticism keeps men sane. As long as you have mystery you have health; when you destroy mystery you create morbidity. The ordinary man has always been sane because the ordinary man has always been a mystic. He has permitted the twilight. . . . He has always left himself free to doubt his gods; but (unlike the agnostic of today) free also to believe in them. He has always cared more for truth than for consistency. If he saw two truths that seemed to contradict each other, he would take the two truths and the contradiction along with them. His spiritual sight is stereoscopic, like physical sight: he sees two different pictures at once and yet sees all the better for that. . . . He admired youth because it was young and age because it was not. It is exactly this balance of apparent contradictions that has been the whole buoyancy of the healthy man.
The whole secret of mysticism is this: that man can understand everything by the help of what he does not understand. The morbid logician seeks to make everything lucid, and succeeds in making everything mysterious. The mystic allows one thing to be mysterious, and everything else becomes lucid. . . . The one created thing which we cannot look at is the one thing in the light of which we look at everything. Like the sun at noonday, mysticism explains everything else by the blaze of its own victorious invisibility.
When I speak to college students, I challenge them to find a single argument against God in the older agnostics (Bertrand Russell, Voltaire, David Hume) or the newer ones (Richard Dawkins, Christopher Hitchens, Sam Harris) that is not already included in books like Psalms, Job, Habakkuk, and Lamentations. I have respect for a God who not only gives us the freedom to reject him, but also includes the arguments we can use in the Bible. God seems rather doubt-tolerant, actually.