“To let understanding stop at what cannot be understood is a high attainment. Those who cannot do it will be destroyed on the lathe of heaven.”
Book XXIII, ¶ 7,as rendered in the epigraph to Ch. 3 of The Lathe of Heaven (1971) by Ursula K. Le Guin, based upon the 1891 translation by James Legge, Le Guin was subsequently informed that this was a very poor translation, as there were no lathes in China in the time of Zhuangzi. The full passage as translated by Legge reads:
He whose mind is thus grandly fixed emits a Heavenly light. In him who emits this heavenly light men see the (True) man. When a man has cultivated himself (up to this point), thenceforth he remains constant in himself. When he is thus constant in himself, (what is merely) the human element will leave him, but Heaven will help him. Those whom their human element has left we call the people of Heaven. Those whom Heaven helps we call the Sons of Heaven. Those who would by learning attain to this seek for what they cannot learn. Those who would by effort attain to this, attempt what effort can never effect. Those who aim by reasoning to reach it reason where reasoning has no place. To know to stop where they cannot arrive by means of knowledge is the highest attainment. Those who cannot do this will be destroyed on the lathe of Heaven.
Original
知止乎其所不能知,至矣。若有不即是者,天鈞敗之。
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Zhuangzi 38
classic Chinese philosopher -369–-286 BCRelated quotes

“Artists who seek perfection in everything are those who cannot attain it in anything.”
Les artistes qui cherchent la perfection en tout sont ceux qui ne peuvent l'atteindre en aucune partie.
Quote, 4 March 1858, from Journal de Eugène Delacroix, book 3
1831 - 1863, Delacroix' 'Journal' (1847 – 1863)

Fourth Mansions, Ch. 1, trans. E. Allison Peers (1961),<!-- Image Books --> p. 77
Interior Castle (1577)
Context: Just as we cannot stop the movement of the heavens, revolving as they do with such speed, so we cannot restrain our thought. And then we send all the faculties of the soul after it, thinking we are lost, and have misused the time that we are spending in the presence of God. Yet the soul may perhaps be wholly united with Him in the Mansions very near His presence, while thought remains in the outskirts of the castle, suffering the assaults of a thousand wild and venomous creatures and from this suffering winning merit. So this must not upset us, and we must not abandon the struggle, as the devil tries to make us do. Most of these trials and times of unrest come from the fact that we do not understand ourselves.

1847
1840s, The Journals of Søren Kierkegaard, 1840s
Context: It is the duty of the human understanding to understand that there are things which it cannot understand, and what those things are. Human understanding has vulgarly occupied itself with nothing but understanding, but if it would only take the trouble to understand itself at the same time it would simply have to posit the paradox.
Source: https://www.vanguardngr.com/2021/03/kidnap-of-schoolgirls-stop-paying-ransom-to-criminals-solanke-tells-fg/ Folake Solanke in 2021 speaking out against the ills in society.

“Peace cannot be achieved through violence, it can only be attained through understanding.”

Quoted in "The Best Liberal Quotes Ever: Why the Left is Right" - Page 39 - by William P. Martin - Reference - 2004