Bonhoeffer Thinking about Friendship

I finished reading Letters and Papers From Prison the other day, and thought before I put it away I would write another couple of thoughts down.

I am much impressed by your remarks about friendship in this connection. As compared with marriage and the ties of kindred, friendship has no generally recognised rights, and is therefore wholly dependent on its own inherent quality. It is by no means easy to classify friendship sociologically.
Perhaps it is a subheading of culture and education, and brotherhood a subheading of the Church, and comradeship a subheading of labour and politics. Marriage, labour, the state and the Church all exist by divine decree. But what of culture and education? I don't think that can be classified under labour, tempting though that may be from many points of view. They belong not to the sphere of obedience, but to that of freedom, which surrounds all three spheres of the divine decrees. The man who is ignorant of this sphere of freedom can be a good father, citizen and worker, and even a Christian, but hardly a complete man and therefore hardly a good Christian in the widest sense of the term.
Our Protestant (not Lutheran) Prussian world has been so dominated by the divine decrees, that it has allowed this sphere of freedom to be pushed into the background. It almost looks today as though the Church alone offers any prospect for the recovery of the sphere of freedom (art, education, friendship and play, 'æsthetic existence' as Kierkegaard called it). I am convinced of the truth of this, and it would help us to a new understanding of the Middle Ages.
What man is there among us who can give himself with an easy conscience to the cultivation of music, friendship, games and happiness? Surely not ethical man, but only the Christian. Just because friendship belongs to this sphere of freedom (the freedom of the Christian man?!) it must be confidently defended against the disapproving frowns of moralism, though without claiming for it the necessitas of a divine decree, but only the necessitas of freedom! I believe that within the sphere of this freedom friendship is by far the rarest and most priceless treasure, for where else does it survive in this world of ours, dominated as it is by the three other decrees?
It cannot be compared with the blessings of the decrees, for it is sui generis [irreducible]; its relation to them is that of the cornflower to the cornfield.

Bonhoeffer, Letters and Papers from Prison, January 23rd 1944