'Aught that a man could or would think of God. God is not at all.'
In other words, God can not be conceptualised or defined in any way at all. This is for a number of reasons: Firstly, God can not by his nature be limited, otherwise nothing new would be able to come into existence. For instance if it were possible for a 1 dimensional being to define God within his 1D world, where he cannot conceive of a 2D or 3D world, then God would not be able to create a 2D or 3D, for if he did then that would mean that the 1D beings definition of God was wrong, as it failed to include the possibility of a 2D or 3D world. Therefore we can confidently state that giving a definition of God is impossible (though thinking 'as God'/being at one with God is not impossible, as that is a matter of alligning your will with Gods, which doesn't require the individual to view God from 'outside'). However identifying fundamental Godlike attributes (eg creating and being) is not impossible, as these are outworkings of Gods will which are manifest in all material and immaterial things.
[As much as it pains me to say this, the Jewish prediliction for identifying God as G-d seems less ridiculous and servile than I used to consider it. By servile, I mean that they are conider themselves so below God, that they cannot even consider the possibilty of identifying him, even for purposes of intellectual debate. ed]
The Myth of the Twentieth Century, Alfred Rosenberg:
'The mystic releases himself more and more from the entanglements of the material world. He recognises that the impulsive aspects of our existence, such as pleasure and power, or even so called good works, are not essential for the welfare of the soul. The more he overcomes earthly bonds, all the greater, richer and more godlike does he feel himself inwardly become. He discovers a purely spiritual power and feels that his soul represents a centre of strength to which nothing can be compared. Such freedom and serenity of soul toward everything, even in the face of god, reveals the profoundest depths into which we can follow the Nordic concepts of honour and freedom. It is that mighty fortress of the soul, that spark of which Meister Eckehart speaks again and again with awed admiration; it represents the most inward, the most sensitive and yet the strongest essence of our race and culture. Eckehart does not give this innermost essence a name, since the pure subject of perceiving and willing must be nameless, without essence, and separated from all forms of time and space. However, today we may venture to describe this spark as representing the metaphysical allegory of the ideas of honour and freedom. In the last analysis, honour and freedom are not external qualities but spiritual essences independent of time and space forming the fortress from which the real will and reason undertake their sorties into the world.'
Honour and Freedom