There is no doubt in my mind that god exists. In fact, every god exists, and every variation of each exists. Every thought that anyone's ever had exists, in the sense that a sketch on a piece of paper exists, in that their existence is subject to the perception and interpretation of them, whereas the paper exists on a lower, more absolute level. Paper, though, it just a name given to a certain range of configurations of molecules, and so it is just as abstract in its own way.
Perhaps "exist" is the wrong word... these things are, they have being, even if that being is not objective enough to fully constitute existence. Then again, for every layer of being, there is a corresponding layer of objectivity, so it could be argued that at any given layer of being, things which are on that level exist, while things that are on higher, more abstract layers merely are. Existence is a subset of being.
Logically, given this model of reality, for any given layer of being, the lower, less abstract things -- while in absolute terms would have some sort of meta-existence -- for all intents and purposes do not exist or have being. That is, they do not exist in the sense that pi does not exist in "2+2=4". While each two may or may not be the area of a circle, of which pi is a factor, pi is not observable as a component of the equation, and has been canceled-out of it if it was ever there. Of course, on lower levels, pi still exists, but as it is not observable from the equation and cannot be proven to exist based upon it, the existence of pi is neither confirmable nor relevant on the layer of the equation, so it is not.
Or perhaps layers are not the best model. Pi and the Golden Ratio can appear in the same equation, both being within a common layer, but each can also appear in its own equation, in which the existence of the other is neither confirmable nor relevant, so while their level of being is at least comparable, it is an oversimplification to say that they are on the same layer, except as part of some perceived and interpreted hierarchy. The existence of the layers is a layer of its own.
Holy crap, that was meta...
Anyway, perhaps a better model is a massive Venn diagram. This diagram would be composed of bubbles of irregular shapes and sizes, intersecting in an infinite number of dimensions, but the dimensions are unimportant. What's important is that, as with any other Venn diagram, there are only four possible relations that any bubble can have to any other: it can intersect it as a peer, it can be a superset that completely contains the other, it can be a subset that is completely contained by the other, or it can have no direct relationship.
In this bubble model, in the context of any given bubble, another bubble is if any part of it is within the context bubble; a bubble's subsets are in the context of that bubble. If it also exists outside that bubble -- that is, they intersect as peers -- the bubble meets the qualifications for objective being; a bubble's peers exist in the context of that bubble. Bubbles with no relation, of course, have neither existence nor being in the context of that bubble, but supersets can only have the irrelevant meta-existence, so these things do not have being or existence either. This all means that in order for A to be, in reference to B, B must include both A and not-A.
Discovery is the expansion of B to include either A or not-A, where before only one was included, and A did not have being in the context of B, either because it had no relationship or because it was a superset.
God -- as an abstract concept -- is, but in the context of humanity, an omnipresent creator of all things can only ever have meta-existence and cannot ever be, and thus is unconfirmable and irrelevant.