ashen cross smudged on the skin
an ancient sign of utter repentance
shaped for one who was broken,
faithful, even repentant for us
[Too often the mystery of God] can become a mystery which arises from ignorance, and the boundaries of human knowledge which remain unanswered. Such was Bonhoeffer's condemnation of a form of mystery in which '[r]eligious people speak of God where human knowledge is at an end (or sometimes when they're too lazy to think further), or when human strength fails'.
The Transfiguration of Jesus
In this kind of mystery ... the God of the Bible is replaced by the human creation of an increasingly superfluous deus ex machina. Human progress in knowledge determines that the space in which so-called 'God' is allowed is rapidly reduced: answering questions of which we are ignorant of the answer, even seemingly ultimate ones, by pointing to a 'God' who fills gaps in our knowledge is no longer possible....
[I]n contrast to this mystery born of ignorance, Bonhoeffer points to the unutterability of God's name within his prison writings. In this discussion, we may find an appropriate form of mystery befitting the very Godness of God. To reclaim this otherness of the God is to begin to move away form a sense that God can ever be captured within the confines of a religion. A theology against religion needs, therefore, to reclaim a true and appropriate doctrine of the mystery of God....
Given that Barth wrote so much, and often did so in such a forthright tone, it might seem surprising that the theme of mystery is pervasive throughout his work. However, Barth constantly affirms the mystery of God throughout Church Dogmatics. For him, crucially, mystery is not an attempt at filling holes that exist in human knowledge; mystery, instead, arises from faith and revelation, rather than from unbelief and ignorance... For him, mystery does not precede revelation; it follows from it....
St. Augustine puts this positively when he speaks of the God not in terms of the darkness of unknowing, but in terms of the one who is so gloriously mysterious that His 'ineffable light beat back our gaze'. The blindingly bright revelation of God is the revelation of the God who makes himself known as the one who is beyond all human comprehension.