Here is an important passage from Moses Maimonides (1138-1204), The Guide to the Perplexed, Dover, p. 80:
It is known that existence is an accident appertaining to all things, and therefore an element superadded to their essence. This must evidently be the case as regards everything the existence of which is due to some cause: its existence is an element superadded to its essence. But as regards a being whose existence is not due to any cause -- God alone is that being, for His existence, as we have said, is absolute -- existence and essence are perfectly identical; He is not a substance to which existence is joined as an accident, as an additional element. His existence is always absolute, and has never been a new element or an accident in Him. Consequently God exists without possessing the attribute of existence. Similarly He lives, without possessing the attribute of life; knows, without possessing the attribute of knowledge; is omnipotent without possessing the attribute of omnipotence; is wise, without possessing the attribute of wisdom: all this reduces itself to one and the same entity; there is no plurality in Him, as will be shown.
God is the Absolute. As such, he is radically other than creatures. God is not just another thing that exists and possesses properties in the way creatures possess properties. He differs from creatures in his mode of existence, his mode of property-possession, his mode of necessity, and his mode of uniqueness. See the following recent posts: God is Uniquely Unique and The Anthropomorphism of Perfect-Being Theology.
Existence accedes to creatures; it is accidental to them. As Maimonides says, existence is "superadded to their essence." This implies a real composition of essence and existence in creatures. But in God there can be no such composition. God does not have existence; he is his existence. As Maimonides puts it, "God exists without possessing the attribute of existence." And similarly for properties such as wisdom and omniscience, etc. God is wise without possessing the attribute of wisdom.
That is a hard saying. Does it make sense? And what sense does it make?
First we need to understand what is being maintained. There are those who will say that there are no properties/attributes but that nonetheless there are true predications. This is the position of the extreme nominalist. Accordingly, 'Socrates is wise' is true but there is nothing in reality picked out by the predicate 'wise' or '___wise' that grounds the correctness of the application of the predicate to the individual. There are predicates but no properties. That is to say: 'Wise' is correctly predicated of Socrates despite the fact that there is nothing in reality that Socrates instantiates or otherwise has in virtue of which Socrates is wise.
This is not what Maimonides is saying. He is not denying that there are properties/attributes. I take him to be saying two things. First, God does not have or possess his attributes. He does not have them by standing in a relation of instantiation to them, nor does he have them as ontological 'parts.' Second, none of the divine attributes is an attribute of creatures.
As for the first point, God does not have his attributes; he is (identically) them. God is radically One. His unity is so 'tight' as to disallow any internal composition or stucturation. And his absoluteness disallows his standing in relation to any properties or factors distinct from him on which he would be dependent for his nature or existence. Thus God does not have existence and wisdom; he is existence and wisdom. The second point, I think, follows from the first: the wisdom of Socrates cannot be the same attribute as the wisdom of God.
On the semantic plane, the two occurrences of the predicate 'wise' in 'Socrates is wise' and 'God is wise' cannot have the same sense. For if they have the same sense, then they pick out the same property; but there cannot be one and the same property of wisdom shared by God and Socrates given that God, but not Socrates, is identical to wisdom. Therefore there is no univocity across the two sentences with respect to the predicate. As I read Maimonides, he holds that 'wise' is equivocal in its human and divine uses.
Maimonides and his fellow travellers on the via negativa are radical foes of even the most sophisticated forms of anthropomorphism. Socrates is powerful. The anthropomorphizer says that God too is powerful and in the very same sense; it is just that whereas the philosopher's power is limited, God's power is maximal. Someone who thinks along these lines is placing God and Socrates on the same scale or order, when God, if absolute and truly transcendent, is "trans-ordinal" to borrow word from Henri Dumery. What the anthropomorphizer does is take some of the attributes of humans and think of God as having those very same attributes.
But if we go the Maimonides route, what do we do with a sentence such as 'God is powerful'? Must we say that it is nonsense? We know what it means to say that Socrates is powerful. But what could it mean to say that God is powerful if the predicate is equivocal across 'Socrates is powerful' and 'God is powerful'? Note also that the subject-predicate form of 'God is powerful' implies a distinction in its truth maker between God and one of his attributes -- in violation of the divine simplicity. How can we think or talk about the simple Absolute if all our thinking and talking must have subject-predicate form (or relational or other forms that require distinctions not applicable to the simple God)?
One response would be to bite the bullet and admit that sentences like 'God is powerful' are, and must remain, strictly nonsensical to the discursive intellect. But this nonsense is not mere gibberish, but a Higher Nonsense, an heuristic nonsense whose function is to point us beyond the limits of the discursive intellect while we are operating within it. From the SEP entry:
As severe as Maimonides' position is, even this is not enough. Although negation is preferable to affirmation, even negation is objectionable to the degree that it introduces complexity: God is neither this nor that. What then? Maimonides' reply (GP 1.58) is that ultimately any kind of verbal expression fails us. Rather than provide a precise metaphysical account of the nature of God, the purpose of theological discourse is heuristic: to “conduct the mind toward the utmost reach that man may attain in the apprehension of Him.” Theological language is important to the degree that it eliminates error and sets us along the path of recognizing God's transcendence. Unless one could speak about God, she could easily fall into the trap of thinking that God is corporeal. But in the end, the only thing it reveals is that God is beyond the reach of any subject/predicate proposition. Thus GP 1.59:Know that when you make an affirmation ascribing another thing to Him, you become more remote from Him in two respects: one of them is that everything You affirm is a perfection only with reference to us, And the other is that He does not possess a thing other than His essence …
Citing Psalm 65, Maimonides concludes that the highest form of praise we can give God is silence.