To know that you do not know is the best.Note the similarity to Chapter 56. Additionally, I've found a quote from the Analects of Confucius that agrees with this.
To pretend to know when you do not know is a disease.
Only when one recognizes this disease as a disease can one be free from the disease.
The sage is free from the disease.
Because he recognizes this disease to be disease, he is free from it.
Say that you know when you do know and say that you do not know when you do not know.Interesting that, for once, they agree. Confucianism is ultimately a pragmatic philosophy, so it is a small wonder that Taoism, Confucianism, Buddhism, and Christianity all seem to agree on this point.