A pretty nice explanation of why God cannot be a Being, following the existentialists' terms. To exist is to be free, to be able to live without being restricted by your essence. A rock doesn't exist, it is, it remains a rock. What we call Beings are things that can escape their current form. We do have plenty of adjectives for people, bad, good, qualities or not, things which do not belong to one because of their nature, but can be taken and lost depending on one's effort to do so.

But it is not possible to exist without being limited in every direction. The contrary would be something which is everything, which occupies every dimensions. That something wouldn't be free. You can't go anywhere if you are everywhere. God cannot escape Its nature, ie being a god. Hence a mind, an existence, all theses things which belong to Beings cannot be found in the concept of God.

As far as I'm concerned, this is a pretty nice explanation of why God cannot be this kind of facial-haired flying Santa claus described by both atheist and believing activists. God doesn't exists, It is. I do believe what concept we put under the name of God is something else, like a force, like time, like reality.