#1. There is a sin unto death, there is a sin not unto death (1 John 5:16-17).
"This sickness is not unto death" (John 11:4), and yet Lazarus died; for when the disciples misunderstood the words which Christ adjoined later, "Lazarus our friend is asleep, but I go to wake him out of his sleep" (11:11), He said plainly, "Lazarus is dead" (11:14). So then Lazarus is dead, and yet this sickness was not unto death; he was dead, and yet this sickness is not unto death. Now we know that Christ was thinking of the miracle which would permit the bystanders, "if they believed, to see the glory of God" (11:40), the miracle by which He awoke Lazarus from the dead, so that this sickness was not only not unto death, but, as Christ had foretold, "for the glory of God, that the Son of God might be glorified thereby" (11:4). Oh, but even if Christ had not awakened Lazarus from the dead, is it not true that this sickness, that death itself, was not a sickness unto death? When Christ comes to the grave and cries with a loud voice, "Lazarus, come forth" (11:43), it is evident enough that "this" sickness is not unto death. But even if Christ had not said these words -- merely the fact that He, who is "the resurrection and the life" (11:25), comes to the grave, is not this a sufficient sign that this sickness is not unto death, does not the fact that Christ exists mean that this sickness is not unto death? And what help would it have been to Lazarus to be awakened from the dead, if the thing must end after all with his dying -- how would that have helped Lazarus, if He did not live who is the resurrection and the life for everyone who believes in Him? No, it is not because Lazarus was awakened from the dead, not for this can one say that this sickness is not unto death; but because He lives, therefore this sickness is not unto death. For, humanly speaking, death is the last thing of all; and, humanly speaking, there is hope only so long as there is life. But Christianly understood death is by no means the last thing of all, hence it is only a little event within that which is all, an eternal life; and Christianly understood there is in death infinitely much more hope than merely humanly speaking there is when there not only is life but this life exhibits the fullest health and vigor.
So then in the Christian understanding of it not even death is the sickness unto death, still less everything which is called earthly and temporal suffering: want, sickness, wretchedness, affliction, adversities, torments, mental sufferings, sorrow, grief. And even if such things are so painful and hard to bear that we men say, or at all events the sufferer says, "This is worse than death" -- everything of the sort, which, if it is not a sickness, is comparable to a sickness, is nevertheless, in the Christian understanding of it, not the sickness unto death.
Despair is the sickness. In Christian terminology death is the expression for the greatest spiritual sickness, and the cure is simply to die, to "die from" despair. The three forms of despair: not being conscious of having a self, not willing to be oneself, but also despair at willing to be oneself. Despair is "sickness unto death." Sin means to be in despair at not willing to be oneself, or to be in despair at willing to be oneself. The lives of most men, being determined by a dialectic of indifference , are so remote from the good (that is, faith) that they are almost too spiritless to be called sinners, almost too spiritless to be called despairers.