The image
In ancient China, crossing a big river was a serious undertaking: boats had to be readied, the right moment awaited, people and goods put at risk. The I Ching takes that experience as an image for any major step: a journey, a project, a decision you can't take back.
The formula
- It is favorable to cross the great river (利涉大川): a good time to commit. It appears in the judgment of Inaction (5), Gathering with Equals (13), Loss, Then Gain (18), Great Achievements (26), Increase (42), Release from Obstacles (59) and Inner Integrity (61), among others.
- It is not favorable to cross the great river (不利涉大川): not now. That's what Conflict, the hexagram of the lawsuit, says.
Sometimes the image shifts from one line to the next. In Nourishment, the fifth line says the river can't be crossed; the sixth says it can. And in Simplicity, the humble person can cross: humility is what makes the crossing possible.
Crossed and not yet crossed
The last two hexagrams, After the End and Transition, are "after crossing" and "before crossing." The book ends, on purpose, with the river still ahead.
In a reading
When this formula comes up, ask: what's your river? If it's favorable to cross, prepare well and take the step. If it isn't, that doesn't mean never; it means not today. The formula often comes with conditions, such as constancy or sincere trust.