Ta-hui Tsung-kao was the first Chinese Ch'an master who emphatically advocated the use of "ts'an hua-t'ou". Criticizing the Ch'an methods of the late Northern and early Southern Sung Dynasties, he said: "Both members of the Sangha and lay people who nowadays devote themselves to religious practice, are committing two great errors:firstly,they tend to study those sayings of others which they regard as something extraordinary; secondly,unable to forget the finger and simply look at the moon,they cannot attain awakening through the sayings of others."
There was a kind of "perverse silent illumina- tion Ch'an" where people were only told to sit calmly without striving for a subtle awakening. Ta-hui claimed that its proponents were,"according to the scriptures, slanderers of great prajna. These people cut down the living wisdom of the Buddhas. They still could not atone for their misdeeds, even if a thousand Enlightened Ones would appear in the world."
Ta-hui did not agree with those who studied the many sayings of others or practiced silent illumina- tion Ch'an,and criticized them on every occasion. Ts'an hua-t'ou was, in his opinion,the best way to practice Ch'an. "A thousand,nay,a ten thousand doubts are only one doubt. If this one doubt is broked by the hua-t'ou,all doubts are broken at the same time. If the hua-t'ou cannot break it,you have to go on with it to the very end. In the event that one discards the hua-t'ou and instead allows doubts to arise based on other's sayings, scriptures, the kung-an's of old or everyday vexations, one becomes a member of Mara's retinue."
Ta-hui instructed his students to practice with the "wu" (does not have) hua-t'ou of "the dog from Chao-chou does not have the Buddha-nature." "Only this one word is the knife with which one's path through `samsara` can be severed. When confused thoughts arise,just pay attention to the word:'wu'. Focus on it in every situation,and all of a sudden one will find that all distorted input has ceased. This is the moment to return home and sit unperturb- ed. "Designed to prevent people from getting lost in the stagnation of silent illumination or the vast bulk of Ch'an School Scriptures, the practice of the "wu" hua-t'ou has opened up a new vista and has provided people with an effective method which leads to awakening. If one is unable to use this hua-t'ou, one can easily proceed into the wrong direction although one invests enormous energy. Ta-hui was convinced that it was the aspect of saving energy which made his practice so powerful,and it was the moment of gaining momentum in which one's efforts were not wasted.
Later hua-t'ous like "The ten thousand things return to one,where does the one return to?" or " Who is mindful of the Buddha?" derived from Ta-hui's Ch'an method which exerted tremendous influence on the post-Sung Ch'an School development in China.