As long as you have faith, you will have doubts. I sometimes use the following illustration when I'm speaking. I tell the audience that I have a twenty-dollar bill in my hand and ask for a volunteer who believes me. Usually only a few hands go up. Then I tell the volunteer that I am about to destroy his (or her) faith. I open my hand and show the twenty-dollar bill. The reason I can say I am destroying his faith is that now he knows I hold the bill. He sees the bill and doesn't need faith anymore. Faith is required only when we have doubts, when we do not know for sure. When knowledge comes, faith is no more.

Sometimes a person is tempted to think, I can't become a Christian because I still have doubts. I'm still not sure. But as long as doubts exist, as long as the person is still uncertain, that is the only time faith is needed. When the doubts are gone, the person doesn't need faith anymore. Knowledge has come.

I tell the audience that this is exactly the point Paul was making in his first letter to the church at Corinth: "Now we see [that a 'knowing' word] but a poor reflection [now we have confusion, misunderstanding, doubts, and questions] … then we shall see face to face [we don't see face-to-face yet]. Now I know in part [with questions and doubts]; then I shall know fully, even as I am fully known" (13:12).