Pope Dionysius

[God] is perfect not only insofar as He is absolute perfection, defining perfection in Himself and from His singular existence and total perfection, but also because He is far beyond being so. He sets a boundary to the boundless and in His total unity He rises above all limitation. He is neither contained nor comprehended by anything. He reaches out to everything and beyond everything and does so with unfailing generosity and unstinted activity.

The fact is that the more we take flight upward [to God], the more our words are confined to the ideas we are capable of forming; so that now as we plunge into that darkness which is beyond intellect, we shall find ourselves not simply running short of words but actually speechless and unknowing.

...God does not possess a private knowledge of Himself and a separate knowledge of all the creatures in common. The universal Cause, by knowing Itself, can hardly be ignorant of the things which proceed from It and of which It is the source. This, then, is how God knows all things, not by understanding things, but by understanding Himself.

...if we know God our knowledge of... everything will be brought to perfection, and, in so far as is possible, the infinite, divine and ineffable dwelling place (cf. Jn. 14:2) will be ours to enjoy. For this is what our sainted teacher said in his famous philosophical aphorism: 'Then we shall know as we are known' (I Cor. 13:12), when we mingle our god-formed mind and divine reason to what is properly its own and the image returns to the archetype for which it now longs.