Of all the things the contemplatives have tried to point at, the ground is the hardest to put a name on. By definition, whatever you can name is already not it. And so the traditions, when they go deep enough, end up doing the same uncomfortable thing: refusing to say.
Lao Tzu refuses with his first five characters. The Kabbalists refuse with Ein Sof, the without-end. Plotinus refuses with his One that cannot have any predicate. The Buddha refuses with sunyata, the open emptiness that is not nothing. Eckhart refuses with the Seelengrund, the ground of the soul, beneath even God’s name for God.
What they are pointing at is not a thing among things. It is what makes thingness possible. To call it being is already to make it less, being is one of the things that comes out of it. The contemplative who has spent long enough in the silence reports back, again and again, that there is a floor that opens beneath the floor, and that the floor that opens is not a noun.
This is the theme the entire perennial conversation orbits. Every other theme, the self, the veil, the return, is finally a particular angle on the same recognition: there is a ground, and the ground is not where you’d expect, and the ground is what you already are.