来书云：「上蔡尝问天下何思何虑。伊川云：『有此理，只是发得太早。』在学者工夫，固是『必有事焉而勿忘』，然亦须识得『何思何虑』底气象，一并看为是。若不识得这气象，便有『正』与『助长』之病。若认得『何思何虑』，而忘『必有事焉』工夫，恐又堕于『无』也。须是不滞于『有』，不堕于『无』。然乎？否也？」
所论亦相去不远矣，只是契悟未尽。上蔡之问，与伊川之答，亦只是上蔡、伊川之意，与孔子《系辞》原旨稍有不同。《系》[1]言「何思何虑」是言所思所虑只是一个天理，更无别思别虑耳，非谓无思无虑也。故曰：「同归而殊途，一致而百虑，天下何思何虑。」云「殊途」，云「百虑」，则岂谓无思无虑邪？心之本体即是天理，天理只是一个，更有何可思虑得？天理原自寂然不动，原自感而遂通。学者用功，虽千思万虑，只是要复他本来体用而已，不是以私意去安排思索出来；故明道云：「君子之学，莫若廓然而大公，物来而顺应。」若以私意去安排思索，便是「用智自私」矣。「何思何虑」正是工夫：在圣人分上，便是自然的；在学者分上，便是勉然的。伊川却是把作效验看了，所以有「发得太早」之说。既而云「却好用功」，则已自觉其前言之有未尽矣。濂溪主静之论亦是此意。今道通之言，虽已不为无见，然亦未免尚有两事也。
来信说：「谢上蔡曾问天下之事何思何虑。程颐说：『有这个道理，只是说得太平早了。』就学者的功夫而言，固然要『必有事焉而勿忘』，但也须认识『何思何虑』的气象，一并看作对才好。若不识得这个气象，便有『正』与『助长』的毛病。若认得了『何思何虑』，又忘了『必有事焉』的功夫，恐怕又堕入『无』了。必须是不滞于『有』，不堕于『无』。对吗？」
所论相去不远了，只是领会未尽。上蔡之问与伊川之答，也只是上蔡、伊川的意思，与孔子《系辞》的原旨稍有不同。《系辞》说「何思何虑」，是说所思所虑只是一个天理，再没有别的思虑罢了，并不是说无思无虑。所以说：「同归而殊途，一致而百虑，天下何思何虑。」既然说「殊途」、说「百虑」，岂是说无思无虑？心的本体就是天理，天理只是一个，还有什么可思虑的？天理原本寂然不动，原本感而遂通。学者用功，虽千思万虑，只是要恢复它本来的体用而已，不是以私意去安排思索出来。所以程颢说：「君子之学，莫若廓然而大公，物来而顺应。」若以私意去安排思索，便是「用智自私」了。「何思何虑」正是功夫：在圣人分上是自然的，在学者分上是勉然的。伊川却把它当效验看了，所以有「发得太早」之说。接着又说「却好用功」，则是已自觉前言有未尽。周敦颐主静之论也是这个意思。如今道通的话，虽已不为无见，然也未免还当作两件事。
Your letter says: 'Shangcai once asked about the line what to think, what to worry. Cheng Yi answered: the principle is there, only it was voiced too early. For learners' work it is surely always having the task at hand and not forgetting; yet one must also know the weather of no-thought-no-worry, holding both as right. Not knowing it, one falls into forcing or aiding growth; knowing it and forgetting the task, one may sink into nothingness. One must neither stick in being nor fall into non-being. Is that so?'
You are not far off; only the grasp is incomplete. Shangcai's question and Cheng Yi's answer are their own sense, slightly off the original purport of Confucius in the Commentaries. There, what to think, what to worry means that all thinking and worry are one heavenly principle, with no other thought or worry — not that there is no thought or worry at all. Hence: same goal, different roads; one accord, a hundred deliberations. With roads and deliberations, how could there be no thinking? The mind's substance is heavenly principle, one alone — what is there to think out? Principle is of itself still and unmoving, of itself stirred and all-penetrating. The learner's thousand thoughts and myriad worries only seek to restore its original substance and function, not something schemed out by private intent — hence Cheng Hao: the noble person's learning is none better than vast impartiality, responding as things come. To scheme and ponder with private intent is wit in selfishness. No-thought-no-worry is itself the work: in the sage natural, in the learner striving. Cheng Yi took it as the fruit, hence 'voiced too early'; his later 'yet good for the work' shows he felt the shortfall. Zhou Dunyi's emphasis on stillness is the same sense. Your words show no little insight, yet you still make two things of it.
- 朱文启校本，「系」下有「辞」字。