It means knowing means knowing, and not knowing means not knowing. Later, it was used to remind people to treat knowledge issues honestly, without any hypocrisy or pride. It is necessary to develop a down-to-earth, serious attitude towards learning, a style of seeking truth from facts, and avoid reckless and grandiose atmosphere.
Confucius advocated that "the known is known, and the unknown is unknown", leaving the unknown aside for the time being.
Attitude, then people below wisdom certainly can't know everything. Admitting what you know and what you don't know is an honest attitude and the smartest attitude, except those mysterious things. Only when he doesn't know, can he know.
Introduction to Confucius:
Confucius was born in Changping Township (now Luyuan Village, Nanxin Town, southeast of Qufu City, Shandong Province). Confucius died at the age of 73 and was buried in Surabaya, north of Qufu, where Kong Lin is now located. Confucius' thoughts on words and deeds are mainly contained in the prose collections "The Analects of Confucius" and "Historical Records of Confucius' Family" preserved in the pre-Qin and Qin and Han Dynasties.
The descendants of the Yin royal family of Confucianism, after the destruction of Yin by the King of Wu, the son of the Yin imperial clan began in the Song Dynasty, and the distant ancestor became a noble in the Song Dynasty. Confucius was born in Shandong, and his status was reduced from a minister to a scholar. At the age of fifteen, Confucius was determined to learn and studied under a teacher. He paid special attention to the etiquette system of the Zhou Dynasty, with the ideal of restoring the "moral politics" at the beginning of the Zhou Dynasty, and was known for his erudition and courtesy for a long time.