Tao Te Ching - Chapter Seventy-One
One who knows what people do not know,
Is a person of enlightenment.
One who pretends to know what he is ignorant of, is at fault.
He who is aware of what he does not know, shall not be at fault.
Therefore, a saint is flawless for he is aware of what he truly knows and what he knows not,
hence he is flawless.