Vjack, the proprietor of Atheist Revolution, presents the following argument from Atheism: The Case Against God:

To be is to be something as opposed to nothing, and to be something is to be something specific. If a god is to have any characteristics (which it must to exist), these characteristics must be specific – but to assign definite attributes, to say that a being is this as opposed to that, is to limit the capacities of that being and to subject it to the uniformity imposed by those capacities. A supernatural being, if it is to differ in kind from natural existence, must exist without a limited nature – which amounts to existing without any nature at all (p. 41).

In other words:

1. To be something is to be something specific
2. Characteristics must be specific and to exist something must have them
   
3. Assigning characteristics to something limits it in some fashion
4. To be supernatural means to exist without limits
5. Therefore, supernatural beings cannot have characteristics, which means that they don’t exist
   
6. God is supernatural
7. Therefore, God does not exist

The logic on this one is tight, and Vjack rightly thinks that there are few ways around this one. He says:

The theist who is not ready to concede defeat has one obvious place of retreat. He or she will claim that his or her god is unknowable. Of course! Theists make this claim all the time. Their god is not merely unknown in the present time but unknowable in principle. The human mind simply cannot comprehend their god. (source)

Human beings are made in the image of God, according to Genesis. Therefore, God isn’t completely unknowable. His actions cannot all be understood by human beings, which is understandable given the infinite nature of God and the finite nature of human beings. I would never say that God is unknowable as an apologetic, however.

Vjack goes on:

As Smith suggests, this shifts the discussion away from metaphysics and back to epistemology. However, before making this shift, it is important to understand that the theist is now admitting that his or her god (and any other supernatural entity) is beyond comprehension of the human mind. Is this really what theists believe? Perhaps it gets them around the many metaphysical problems with their god, but it may well come back to haunt them. (source)

He clarifies what he means in an imaginary dialog between an atheist and a theist where the theist is forced to admit that he has no idea what he believes in, since God is unknowable. This trap is exactly why I would avoid simply saying “God is unknowable” as an apologetic.

How do I answer this dilemma? Well, for one thing, I would take issue with statement #4. Why does a supernatural being have to exist without limits? Epistemologically, we only know the natural world. It is impossible for us to perceive the supernatural. So we don’t know that that statement is true. Since #4 cannot be proven, you cannot conclude #5. The rest of the logic chain falls apart.

But this still raises an interesting question. Does God exist without limit? Because if he does truly exist without a limit, then he has no limiting characteristics and therefore exists with no nature at all. And that is a logical impossibility.

Well, we know that God cannot lie (Tts 1:2, Heb 6:18). There’s at least one limiting characteristic. There are other characteristics of God. In fact, I have a book that lists over 100 attributes. Surprisingly, in that book, “Limitless” doesn’t appear. That is because God isn’t limitless, he is infinite.

“Limitless” and “infinite” are distinct from one another. We’ve already seen that a being that exists without limits is a logical impossibility. Infinite, in the sense of everlasting, is not a logical impossibility. It is hard for us to grasp, but it isn’t impossible. God is the Alpha and Omega, the first and the last. He is eternally self-existent. These are not logical impossibilities, but they are hard to for a finite mind to understand.