A few friends recently mentioned struggling with doubt. Of course, there are many kinds of doubt. Some doubts constitute certifiable existential crises. Often, one can become profoundly inconsolable in doubt. Paradoxically, we begin to take comfort in our uncertainties. We can become attached to our doubts and fearful of what their assuagement might imply. Worse, we might try to rationalize irresponsibility and sin by appealing to overwhelming doubt.
When I was a second-year college student in 1993, I read Os Guinness' "Faith In Two Minds: The Dilemma of Doubt." It has since been re-published (and revised, I think) as "God In The Dark." I appreciated most things he had to say in the book, and I recommend it to you all. I found it helpful in thinking through the issue in general, and my own doubts in particular. I also refer you back to my post on assurance, of 24 September.
Doubt is not, in every case, a bad thing. It largely depends on what is being doubted, and what effect this doubting has. When it concerns God and Scripture, we must keep in mind that "whatever is not of faith is sin."
It may be helpful to consider that doubting may be based in opinion. That is, sometimes we confuse doubt with not having an opinion on a matter. And, I think, doubt is often related to probability. That may be obvious, but it may be helpful to seek resolution to doubts in terms of examining "relative likelihood." And remember that God never doubts because, in the most ultimate sense, there are no probabilities.