Theologian Os Guinness once wrote, 

"If ours is an examined faith, we should be unafraid to doubt. If doubt is eventually justified, we were believing what clearly was not worth believing. But if doubt is answered, our faith has grown stronger. It knows God more certainly and it can enjoy God more deeply."

 Many of have wrestled and are still wrestling with doubt, as have not a few of the wisest minds in Christendom. I believe George MacDonald would heartily concur with Os. And among those he influenced, G.K. Chesterton and C.S. Lewis had profound thoughts on the subject. 

What passages on doubt from MacDonald, Chesterton, Lewis, and others have been significant to you? And what has been your experience dealing with doubt in your own life or in helping others?