It is a metaphor for people's turning back and deciding life and death.
First, the source: Xunzi. Mourn for the public. "
Second, the original text:
Out of the fourth gate of Lu, you can see the suburbs of Lu. If you are afraid of national subjugation, you must hide it. I'm afraid to think about it. And autumn patterns, monarch, boat also; Shu Ren, water also.
The knife cuts bread and fingers. What if you think about danger with this? "