Shinji Shobogenzo, Book 1, Case 13

A monk asked Master Jisai – “How is the moon when not yet round?”

The master said, “swallowing three or four moons”

The monk said, “And when the moon is round?”

The master said, “vomiting seven or eight moons”.

In this story the moon is a symbol of enlightenment, so the monk’s question really is: what is the person like before and after enlightenment?

The Master’s answer seems to be that before enlightenment the person is primarily conceptual. So, the various concrete moons the person experiences – the harvest moon, the waxing moon, the present moon and so on – all arise within [swallowed] the concept of ‘moon’, whereas for the enlightened person, the actual limitless manifestations of moon are – as it were- liberated [vomited] from the concept of moon.

This interpretation isn’t wrong but it can lead to a terrible literal Zen, where there is an unbalanced emphasis is on concrete reality and a lot of banal and formulaic talk about the Here and Now. And in this block of concrete Zen, delusion is considered as the other: thoughts, dreams, imaginings, visions and so on.

In his commentary on this koan, Dogen says that the whole world is expressed in the act of swallowing and the whole world is expressed in the act of vomiting. We should swallow the self and the whole world. We should vomit the self and the whole world

Or, to put it slightly differently – there is a dynamic folding and re-folding between wholeness-ising everything [swallowing], and releasing everything in its own vivid expression-ing [vomiting]

Which is our practice.