Chapter 71
第七十一章
To know and yet (think) we do not know is the highest (attainment);
知不知，尚矣；
not to know (and yet think) we do know is a disease.
不知知，病也。

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.
圣人不病，以其病病。
He knows the pain that would be inseparable from it, and therefore he does not have it.
夫唯病病，是以不病。