And faith is concerned with a decision once for all. Faith is not an opinion replaceable by another opinion. A temporary believer does not know what faith is. Faith means a final relationship. Faith is concerned with God, with what He has done for us once for all. That does not exclude the fact that there are fluctuations in faith. But seen with regard to its object, faith is a final thing. A man who believes once believes once for all. Don't be afraid; regard even that as an invitation. One may, of course, be confused and one may doubt; but whoever once believes has something like a character indelibilis. He make take comfort in the fact that he is being upheld. Everyone who has to contend with unbelief should be advised that he ought not to take his own unbelief too seriously. Only faith is to be taken seriously; and if we have faith as a grain of mustard seed, that suffices for the devil to have lost his game.
One could make a mistake here and think he's talking only in Calvinist terms of the Perseverance of the Saints--I don't think that's quite his point. It's too easy, anyway, to look for slogans or confessional stances and so read "the meaning" of a text as opposed to what it says. His starting point is the individual experience--ultimately his--which is then given the language available to describe it. To not have this belief is to despair--if faith is really freely able to be rejected and taken back at all times, that's not really faith. But even the person who accepts a rejection-and-return model follows Barth, for the rejection and the return both take place in an institutional context which is never left, even when faith, on that model, is gone. Agreeing to that, the discussion can then turn to better and worse models of faith and its relation to the rest of life.