God.

God, in the holy tongue, they call
The place that filleth all in all.

In God there's nothing, but 'tis known to be
Even God Himself, in perfect entity.

God, as the learned Damascene doth write,
A sea of substance is, indefinite.

God is not only said to be
An Ens, but Supraentity.

That there's a God we all do know,
But what God is we cannot show.

God is above the sphere of our esteem,
And is the best known, not defining Him.