The opposite of faith in scripture is not doubt but anxiety. To lack faith is not so much to have theoretical doubts about God's existence as it is to be anxious and fearful at a deep level.
How is this possible? We cannot help but be full of anxiety and worry about many things — our loved ones, our health, our work, our future: “Will I pass this examination?” “Will my son come home this evening?” “Will my medical check–up be okay?” “Will this person reject me?” “Will I lose my job?” “Will I get this promotion?” “Can I pay my mortgage?” “Are my daughter's new friends good for her?” “Is my spouse being truthful?” “Do people like me?” “Are my clothes right?” “Will I be stuck in traffic and miss my appointment?” There is rarely a moment in our lives that is not clouded by a worry of some kind or other. We are always somewhat anxious. Is worrying about so many things bad for our faith?
Not necessarily. What opposes faith is not so much worry about this or that particular thing as worry that God has forgotten us, worry that our names are not written in heaven, that we aren't in good hands, that our lives aren't safe, and that there is every reason to fear and be anxious because, at the core of things, there isn't a benevolent, all–powerful goodness who is concerned about us.
Our anxiety opposes faith when, however vaguely we might have this feeling, we have the sense that God is not fully trustworthy or powerful enough to assure that, as Julian of Norwich so wonderfully puts it, in the end all will be well and every manner of being will be well.
Perhaps this can be best explained by looking at its opposite. In the Garden of Gethsemane, Jesus is surrounded by darkness and betrayal. He has, it seems, every reason to be deeply anxious. Yet, he begins his prayer with the words: “Father, all things are possible for you!” On the surface, all is terror, but underneath there is a rock–solid trust. He senses God's graciousness and power, despite the darkness. Our problem is often the opposite. We are surrounded with light (love, trust, health, good cheer, and no immediate danger or threat) yet underneath are racked with fear, guilt, and distrust. Jesus stood inside of darkness and was secure in the light, we stand in the light and are anxious about a darkness underneath; Jesus was being put to death by sick forces and he rooted himself in the sense that things are still good, we stand inside of health and feel guilty about life's goodness; Jesus was dying and he assured himself that God had not forgotten him, we wake up to sunshine on any given morning and worry that we have been forgotten.
Have you ever had the experience of going to your closet and noticing an item of clothing that you had forgotten you still possessed? You see a shirt or a blouse that you haven't worn for a long time and you say to yourself: “I still have this! I had completely forgotten about it!” It had simply slipped off your radar screen. Anxiety of this sort is what haunts faith, the fear that we have slipped off God's radar screen, that we have been forgotten, that God will look down on earth sometime and realize with a start that we are still here: “My God, she's still there. I had completely forgotten about her!” It is this kind of anxiety, the deep fear that we have been forgotten, that so much pushes us to make an assertion of our lives. Nobody wants to live and die unnoticed, insignificant, forgotten. We are always somewhat anxious about that. This anxiety is the opposite of faith, not so much the fear that God doesn't exist as the fear that God does not notice our existence.
What is faith? Faith doesn't have you believe that you will have no worries, or that you will not make mistakes or betray, or that you and your loved ones won't sometimes too fall victim to accident, sickness, and suicide. What faith gives you is the assurance that God is good, that God can be trusted, that God won't forget you, and that, despite any indication to the contrary, God is still solidly in charge of this universe. Faith says that God is real and God is lord and, because of this, there is ultimately nothing to fear. We are in safe hands. Reality is gracious, forgiving, loving, redeeming, and absolutely trustworthy. Our task is to surrender to that.
Faith assures us that there is really nothing to fear. We see this in scripture: Virtually every time that God appears in revelation, when heaven speaks to earth, the opening words are: “Do not be afraid! Be at peace!”
Those words capture what faith ultimately invites us to.