Missionarying was a better thing in those days than it is in ours. All you had to do was to cure the head savages sick daughter by a miracle- a miracle like the miracle of lourdes in our day, for instance- and immediately that head savage was your convert, and filled to the eyes with a new converts enthusiasm. You could sit down and make yourself easy now. He would take the ax and convert the rest of the nation himself.
So to be sick unto death is, not to be able to die-yet not as though there were hope of life; no, the hopelessness in this case is that even the last hope, death, is not available. When death is the greatest danger, one hopes for life; but when one becomes acquainted with an even more dreadful danger, one hopes for death. So when the danger is so great that death has become one's hope, despair is the disconsolateness of not being able to die.