If Yí has appeared in your reading, the book is naming a moment to attend to the channels of nourishment. The shape of the hexagram is the shape of an open mouth — yang lines top and bottom, yin lines in between. Food enters here. Words leave here. The discipline is the same in both directions.

Classical commentary reads this hexagram broadly. Nourishment is not only food. It is what the eye consumes, what the ear listens to, what the company around you supplies. It is also what you supply in return — your speech, your attention, your effects on others. The hexagram appears when the channels themselves have come due for inspection.

What the book counsels is the careful examination of source. 自求口實 — seek what fills the mouth from oneself. Not self-sufficiency in the modern sense; rather, the responsibility for what one consents to be fed. The reader is being asked to notice what is being put on the table — the literal table, the screen, the conversation — and to choose accordingly.

Yí's failure mode is passive consumption: taking in whatever is set before one without registering what the diet is doing. The book is alert to this. The hexagram appears when the reader has been letting the channels run on autopilot. The work is to bring attention back to them, on both sides — what comes in, what goes out, and whether either is what the body actually needs.