After counseling us to let go of wisdom, of the display of morality and of cunning, Lao Tzu names what is to be held on to.
He uses two images: undyed silk and the uncarved block.

Both are the state before anything is added.
So too a person is whole before being adorned, before being cut to shape.

The second half of the line gives the way: as the self grows smaller and desire grows thin, that first plainness comes forth of itself.