“The vow is to the man what the song is to the bird, or the bark to the dog; his voice, whereby he is known.  Just as a man who cannot keep an appointment is not fit even to fight a duel, so the man who cannot keep an appointment with himself is not sane enough even for suicide.  It is not easy to mention anything on which the enormous apparatus of human life can be said to depend.  But if it depends on anything, it is on this frail cord, flung from the forgotten hills of yesterday to the invisible mountains of tomorrow.”  G.K. Chesterton, The Appetite of Tyranny