知无不言,言无不尽 Say all one knows, and say it without reserve. The Song writer Su Xun used the words for the bond between a ruler and his most trusted minister.
In On Coalition Government, in 1945, Mao Zedong joined it with two other sayings: “Those who speak are not guilty, and those who hear take warning,” and “Correct mistakes if there are any, and if there are none, take it as encouragement.” He called them “useful maxims of the Chinese people.”
In 1957, a Party directive on the rectification campaign called for encouraging criticism and practicing these principles firmly. In 1977, the first two were written into the Party Constitution.