"Talk about the death of God is not entering theology for the first time in our century; rather it is returning home to theology. Talk about the death of God was not at all alien to Christian theology originally. The fathers of the ancient church could talk about it, and Martin Luther virtually demanded that it was necessary to speak of the death of God, using, of course, very precise presuppositions. The statement 'God has died' was not originally the province of philosophy but of theology. Then it became alien to theology." -- Eberhard Jüngel, God as the Mystery of the World (GMW)
In the 1960's and '70's, it was common for avant-garde theologians to proclaim that "God is dead!". Jüngel makes it clear in GMW that he has a very low opinion of this type of theology, remarking that "the motto 'God is dead' can be used to make theological thinking unbelievably simple", and "not a few theologians who began to be somewhat embarrassed about their actual task now used the statement as a kind of fig leaf in order to conceal the nudity of their theology behind it." However, Jüngel maintains that theology needs to seriously contemplate the implications of God's death, not because modern atheism demands it, but because the concept has its origin in the Crucified God.
It was Bonhoeffer's prison writings that "prepared the way for the return home to theology of talk about the death of God":
"[Bonhoeffer] proposed that the atheistic thought of the nonbeing of God should be so worked through theologically that the Christian faith could receive elements of truth from atheistic religionlessness and work them into the Christian concept of God... God's true deity is demonstrated for Bonhoeffer in the very fact that he permits himself to be expelled from the world. The concept of weakness enters the concept of the divine essence - and as a consequence, the concept of death."
Jüngel makes the case that, for too long, Christian theology has derived its notions of God from speculative metaphysics, which holds that God is omnipresent, omniscient, all-powerful, unchanging, and completely transcendent. For such thinking, the death of God is simply impossible. But the Christian proclamation asserts that God, through Jesus Christ, experienced death on the cross, and thus God's self-revelation in the cross requires that we modify our thinking about God. Theology must continually ask itself the question: What does it say about the nature of God if he can die a human death? Certainly, he is not the God of the philosophers, which Christians have mistakenly made their own. And he is not the God that atheists have rejected. The Christian God, according to Jüngel, is neither the God of theism or atheism, but something entirely different.
It's interesting that both Jüngel and Tillich are eager to move beyond the God of traditional theism, but for opposite reasons. For Tillich, the need for a "God above the God of theism" is motivated by the same philosophical considerations that Jüngel so strongly rejects. In this way, Tillich's doctrine of God is apologetic through and through, since he is making a "case for God" using universal categories. Jüngel, on the other hand, grounds his thinking in the scandal of the cross, and he's adamant that he "does not intend to provide an apologetic for Christianity." He is "occupied with talk about the death of God because of the theological relevance of the problem concealed in such talk, but not for apologetic reasons." Jüngel believes that it was not humans who killed God (as Nietzsche asserted), but that God gave himself up to death out of pure love for the man Jesus. Only in this manner is talk of the death of God meaningful for theology.