Doubt is not the opposite of faith, nor is it the same as unbelief. Doubt is a state of mind in suspension between faith and unbelief so that it is neither of them wholly and it is each only partly. This distinction is absolutely vital because it uncovers and deals with the first major misconception of doubt—the idea that we should be ashamed of doubting because doubt is a betrayal of faith and a surrender to unbelief. No misunderstanding causes more anxiety and brings such bondage to sensitive people in doubt.
The difference between doubt and unbelief is crucial. The Bible makes a definite distinction between them, though the distinction is not hard and fast. The word unbelief is usually used of a willful refusal to believe or of a deliberate decision to disobey. So, while doubt is a state of suspension between faith and unbelief, unbelief is a state of mind that is closed against God, an attitude of heart that disobeys God as much as it disbelieves the truth. Unbelief is the consequence of a settled choice. Since it is a deliberate response to God’s truth, unbelief is definitely held to be responsible. There are times when the word unbelief is used in Scripture to describe the doubts of those who are definitely believers but only when they are at a stage of doubting that is rationally inexcusable and well on the way to becoming full-grown unbelief. Thus the ambiguity in the biblical use of unbelief is a sign of psychological astuteness and not of theological confusion.
So it is definitely possible to distinguish in theory between faith, doubt, and unbelief (to believe is to be in one mind, to disbelieve is to be in another, and to doubt is to be in two minds). But in practice the distinction is not always so clear-cut, especially when doubt moves in the direction of unbelief and passes over that blurred transition between the open-ended uncertainty of doubt and the close-minded certainty of unbelief.
But the overall thrust of the biblical teaching on doubt is plain. A variety of words are used but the essential point is the same. Doubt is a halfway stage. To be in doubt is to be in two minds, to be caught between two worlds, to be suspended between a desire to affirm and a desire to negate. So the idea of “total” or “complete” doubt is a contradiction in terms; doubt that is total is no longer doubt, it is unbelief.
Of course, we may call our doubt “total doubt” or charge it with being unbelief. But only if our purpose is to stop doubt short and see that it does not become unbelief. When the father of the demoniac boy cried out to Jesus, “I believe; help my unbelief!” he was condemning his own doubt as unbelief. But Jesus, who never responded to real unbelief, showed by answering his prayer and healing his son that he recognized it as doubt. The distinction between doubt and unbelief, though not hard and fast, is valid and useful. Its importance, however, is not that we know when doubt becomes unbelief. Only God knows that, and human attempts to say so can be cruel. But it means that we should be clear about where doubt leads to as it grows into unbelief.
Excerpt from “God in the dark” by Os Guinness