Excerpt from John Hick's site - John Hick:
But Dionysius ... makes the divine ineffability central and begins at least to struggle with its implications. In his central work, The Mystical Theology, he says in every way he can think of that God is utterly and totally transcategorial. God is ‘indescribable’, ‘beyond all being and knowledge’. God, the ultimate One, is ‘not soul or mind, nor does it possess imagination, conviction, speech, or understanding. . . It cannot be spoken of and it cannot be grasped by understanding . . It does not live nor is it life. It is not a substance, nor is it eternity or time. It cannot be grasped by the understanding . . It is neither one nor oneness, divinity nor goodness . . It is not sonship or fatherhood . . There is no speaking of it, nor name nor knowledge of it . . It is beyond assertion and denial’.
And Hick's commentary on the quoted passage:
This last statement, that that to which the term ‘God’ refers is beyond assertion and denial is crucial. For (Denys) is not simply doing negative theology, saying that God does not have this or that attribute but, much more radically, that our entire range of attribute-concepts do not apply to God at all, either positively or negatively. To apply them to God in God’s ultimacy is, in modern philosophical terms, a category mistake. To say, for example, that molecules are not stupid, although true, is misleading because it assumes that molecules are the sort of thing of which it makes sense to say that they are either stupid or not stupid. And to say that God is not ‘one nor oneness, divinity nor goodness’, although true would likewise, by itself, be deeply misleading because it assumes that God is the kind of reality to which such qualities could be rightly or wrongly attributed. We have to take on board the much more radical concept of a reality which is what it is, but whose nature lies beyond the scope of our conceptual and linguistic systems. When we speak about such a reality we are not, then, speaking about it as it is in itself, totally beyond the range of our comprehension, but about its impact upon us, the difference that it makes within the realm of human experience, to which our concepts and hence our languages do apply.