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.
About the text, translation & sources
The Chinese text follows our sister site, Longhu Mountain. The English is James Legge’s public-domain translation, first published in 1891, transcribed from the Project Gutenberg edition. Paragraph numbering is omitted; wording, parenthetical explanations and period language are retained. Chinese readings vary between editions.
The Tao Te Ching is traditionally attributed to Laozi. Its date and authorship are debated. Chapter titles are reading aids; they are not part of the ancient Chinese chapter text. The reflection boxes on this site are contemporary editorial questions, distinct from the translation.