To know that you do not know is the highest attainment. To not know and yet think you know is a disease. Only by recognizing the disease as a disease can one be free from it. The Sage is not diseased because he recognizes the disease as a disease; therefore, he is not diseased.
To know that you do not know is best; to not know yet think you know is a disease. The Sage is free from disease because he treats the disease as a disease.