The great Swiss theologian  addresses the task of preaching, from a late-career book of the same name:

barth“A fourth consequence [of God’s humanity]: the sense and sound of our voice must be fundamentally positive. Proclamation of the covenant of God with man, announcement of the place which is once for all opened and assigned to man in this covenant, the message of Immanuel, the message of Christ – this is the task. The dialogue and encounter which are our theological theme involve God’s grace and man’s gratitude. To open up again the abyss closed in Jesus Christ cannot be our task. Man is not good: that is indeed true and must once more be asserted. God does not turn toward him without uttering an inexorable ‘No’ to his transgression. Thus theology has no choice but to put this ‘No’ into words within the framework of its theme. However, it must be the ‘No’ which Jesus Christ has taken upon Himself for us men, in order that it may no longer affect us and that we may no longer place ourselves under it. What takes place in God’s humanity is, since it includes that ‘No’ in itself, the affirmation of man.

The direction of our word is given therewith. The man with whom we have to do in ourselves and in others, though a rebel, a sluggard, a hypocrite, is likewise the creature to whom his Creator is faithful and not unfaithful. But there is still more: he is the being whom God has loved, loves, and will love, because He has substituted Himself in Jesus Christ and made Himself the guarantee… And with this explanation the statement that the human spirit is naturally Christian may also be valid as an obstinately joyful proclamation. That is what we have to testify to men in view of the humanism of God, irrespective of the more or less dense godlessness of their humanism – everything else must be valid only in the framework of this statement and promise.”