Written in the 6th century B.C. by Lao Tsu with three English translations show here.
Not-knowing is true knowledge.
Presuming to know is a disease.
First realize that you are sick;
then you can move toward health.
The Master is her own physician.
She has healed herself of all knowing.
Thus she is truly whole.
Knowing ignorance is strength.
Ignoring knowledge is sickness.
If one is sick of sickness, then one is not sick.
The sage is not sick because he is sick of sickness.
Therefore he is not sick.
To know and yet think we do not know is the highest attainment; not to know and yet think we do know is a disease.
It is simply by being pained at the thought of having this disease that we are preserved from it.
The sage has not the disease. He knows the pain that would be inseparable from it, and therefore he does not have it.