I will concede that he does exist for the simple fact how can there be any kind of in-depth discussion on God if we are still arguing weather God exists or not.
Until we've established that he actually exists, why would we want to have an "in-depth discussion" of God?
The greatest fault with religion/theology is that it doesn't even bother to establish the existence of the thing it claims to study, it just skips ahead to presuming the qualities of that entity. I think the conversation should remain at the level of "does God exist or not" until that issue is settled. And if it's settled on the side of "no, he doesn't" then I don't see what further conversation is to be had, aside from "if God doesn't exist, why is the deluded belief in him so widespread?"
This has been a good thing for our species in many circumstances but in the case of God the ability to define or even name him is an impossibility.
Why? His name is "God", and he could be defined as "the mythical being who is the focus of several of the world's religions and suggested to be the creator of all things." There's absolutely nothing mysterious about God. It's a perfectly simple concept. The sense of "mystery" is really nothing more than the mental tension created by fervent belief in an obvious falsity.
Me saying that you are human only says that you are not a dog,horse,cow,etc.
No, quite the opposite. You could say that I was not a dog, not a horse, not a cow, and you'd have to go on down the list of 100 million different species or so. Saying that I'm "human" is saying what I am; being human is more than not being not human.
I mean by your construction it's simply impossible to define anything "in terms of what it is", since every positive term connotes the absence of that term's opposites. (I mean "positive" in the sense of "making a logically positive claim", not "positive" as in "favorable" or "good.") I can't say you're greedy without saying you're not charitable, but that doesn't mean that the term "greedy" only describes you in terms of what you're not. There's more to being greedy than simply not being not greedy.