Tao can be talked about, but not the Eternal Tao.
Names can be named, but not the Eternal Name.
As the origin of heaven-and-earth, it is nameless:
As “the Mother” of all things, it is nameable.
So, as ever hidden, we should look at its inner essence:
As always manifest, we should look at its outer aspects.
These two flow from the same source, though differently named;
And both are called mysteries.
The Mystery of mysteries is the Door of all essence.