This expression refers to a cognitive state which is completely clear and penetrating. It was proposed by Xunzi (313?-238 BC). He felt that people could understand human relations in daily life through the use of the “mind” (xin心), but the mind was often clouded by various factors. Xunzi advocated lifting the clouds by keeping the mind open, concentrated and tranquil, which would lead to a clear and penetrating understanding of human relations in daily life. Such a cognitive state is that of great clarity and brightness.

Keeping the mind open, concentrated and tranquil when one tries to understand general rules – this is called great clarity and brightness. Xunzi