George H. Smith in his book Atheism: The Case Against God  wishes to analyze the Christian concept of God by examining its very nature. Introducing this analysis, he opens with a clarification:
Traditional Christianity offers us two basic ways in which we may discuss the nature of God: (a) negatively, by stating what God is not, referred to as negative theology; (b) positively, by stating what God is, referred to as affirmative theology. Some theologians have adopted negative theology exclusively, while others have employed a combination of both. Our concern is with evaluating the success of these approaches in explaining how man can know an unknowable God. 
Immanuel Kant in Lectures on Philosophical Theology , and his discussion on the knowledge of God distinguishes between these two phenomenons of knowledge: “Positive knowledge is very limited, but this makes the gain of negative knowledge so much greater. As regards positive knowledge of God, our knowledge is no greater than ordinary knowledge. But our negative knowledge is greater” . A simple contrast between the two, but the significance according to Kant is remarkable. “What interest does reason have in this knowledge? Not a speculative, but a practical one. [ … ] [O]ur morality has need of the idea of God to give it emphasis. Thus it should not make us more learned, but better, wiser, and more upright” .
However, the problem Smith finds with these matters of our knowledge of God and his very characteristics “simply push the idea of God beyond man’s comprehension” . To demonstrate the point of Smith, consider a view given matters of our own knowledge:
- (a) Man, when he perceives of reality, is aware of a finite and limited existence;
- (b) Man perceives material organism with limited capacities;
- (c) Man perceives a world of change;
- (d) Man perceives a knowable and natural universe.
However, in respect to defining God with negative terminology Smith calls this the “non-everything-man-knows” technique. For instance, (a) Man perceives a finite and limited existence, (a’) but God is infinite and unlimited. (b) Man perceives material organisms with limited capacities, but (b’) God is immaterial with unrestricted capacities. (c) Man perceives a world of change, but (c’) God is unchanging. (d) Man perceives a knowable and natural universe, but (d’) God is unknowable and a supernatural being. Thus, after this sort of epistemological conundrum, Smith writes that “God is the negation, the exact reversal, of how man perceives reality” .
However, Aquinas’ solution to the analogical use of language seems to have taken care of this problem. In other words, our coherent mode of language is based on a resemblance between God and finite creatures. However, Smith objects that such a resemblance is impossible. He writes:
We must remember that a supernatural being differs in kind from finite existence, not merely in degree. This unbridgeable gap between God and man prevents the Christian from arguing that God possesses the same qualities as man, but to a greater extent [ … ] [T]he “goodness” of God is not the goodness of man magnified to a tremendous degree, nor is the “intelligence” of God a kind of exaggerated human genius. God and man are diametrically different species, so there can be no intrinsic similarities between the attributes of God and the attributes of man. We see, therefore, that the analogy between God and man cannot stem from similarities in their natures. No such resemblance is possible. 
Thus, any understanding of God with these such attributes seem to be caught within the error of inconsistency. However, a critique of Smith’s position might be something more so of his mistake on the preliminaries.
A Critique of Smith’s Objection
Referring back to Smith’s comment that “the analogy between God and man cannot stem from similarities in their natures,” it should be important to note how our knowledge is as such. Thomas Aquinas once noted that intellectual cognition is dependent on sense experience. (e.g., “It is natural to human beings to attain to the intelligible though sensible things.”) Jan Aertsen explains this point:
[s]ystematic knowledge extends only as far as sensory cognition. Of course, the senses are not the total cause of all our knowledge, but they do provide the indispensable material from which the intellect abstracts the intelligible content. From this it follows that human beings cannot know the essence of a substance that is not perceptible by the senses. 
It is thus Aquinas’ position that “in this life we cannot see God’s substance but know him only from creatures: as their non-creaturely and transcendent.” In other words, we know God through his effects, or in his relation to the created order. Mortimer Adler in his interview with William Buckley recognizes three things that we can know positively about God: (1) God knows, (2) God wills and (3) God exists. Aquinas goes even further so as to say that (4) God is good and (5) God is wise, but nonetheless, this knowledge we have of God in some instances can be rationally verified on the basis of reason and other on the basis of revelation (e.g., wisdom, holiness, etc.).
Smith more so may be critiquing an Anselmsian position with the loss of his focus on the critique of analogy. I do believe however, that he has failed in his critique on the language of analogy .
-  George H. Smith, Atheism: The Case Against God (Promotheus: 1979)
-  Ibid., p. 51
-  Immanuel Kant, Lectures on Philosophical Theology, trans. by Allen W. Wood and Gertrude M. Clark (Cornell University Press: 1978)
-  Ibid., p. 24
-  Ibid.
-  Smith, 53
-  Ibid.
-  Ibid., p. 57
-  Jan Aertsen, Aquinas’s Philosophy in its Historical Setting in The Cambridge Companion to Aquinas (Cambridge University Press: 1997) p. 32
-  For more on Aquinas’ position, see my other post on Aquinas at https://philosophicaugustine.wordpress.com/2013/07/23/thomas-aquinas-on-religious-language/