The Analects of Politics
Note: this sentence has five words "know". The first four words all mean "know", and the last one is the same as "wisdom" and "cleverness".
Knowing is knowing, and not knowing is not knowing. This is a smart attitude.
When commenting on Confucius' education for students, we should adhere to an honest learning attitude. Understanding is understanding, not understanding is not understanding, and we have to pretend not to understand. Learning is like this, and so is other aspects!