"[1][2] Shenhui is notable for his strident attacks on Yuquan Shenxiu and the associated "Northern School", which was the most prominent branch of Chan Buddhism in China at the time.

Shenhui then bowed and returned to his seat, but Huineng then proclaimed, "In the future if this youngster heads a monastery, it will certainly bring forth fully realized disciples of our school."

Despite his attacks on the Northern School, Shenhui traveled north to live amongst his ideological enemies in the capital city of Luoyang.

During the An Lushan Rebellion, monks were asked to lecture, and sell certificates to the public in order to raise money for the counteroffensive.

[9] It was presented in the form of a discussion between him and a monk named Chongyuan, who took the side of Shenxiu's Northern School.

He also accused "Northern School" students of trying to steal Bodhidharma's robe, to sever the head of Huineng's mummy, and to rewrite the inscription on Shenxiu's tomb with the words "Sixth Patriarch".

[12]: 111 However, some scholars indicate that Shenxiu's extant writings do not support the view that he rejected sudden enlightenment.

Indeed, according to McRae, Shenxiu's Guanxin Lun (觀心論; Treatise on the Contemplation of the Mind) states: “It does not take long to witness this; enlightenment is in the instant.

Why worry about your white hair (i.e., about your age)?”[13] Several scholars consider Shenhui's arguments against the "Northern School" to be fabrications or exaggerations.

[11]: 113–114 Scholars such as Philip Yampolsky have suggested that one of his disciples may have written the Platform Sutra, which glorifies Huineng and "sudden" enlightenment while deriding Shenxiu.

Scholars note that both the concept of a "patriarch" and the possession of the robe of Bodhidharma being the indicator of this person probably arose as a result of Shenhui's diatribes.

[14] In elucidating his position of sudden enlightenment, Shenhui explained the difference between the teachings of Huineng and Shenxiu in the following exchange with Dharma Master Chongyuan: Dharma Master Chongyuan asked, “Why shouldn’t one [regulate] the mind to realize the internal?” His Reverence replied, “That is the teaching of fools!

[16] For Shenhui, activating intentions to grasp bodhi, nirvana, emptiness, purity, or concentration were all examples of the false mind.

[24] For Shenhui, the disappearing of thought with awareness is "precisely [what is meant by] the non-abiding mind of one’s original nature.

For concentration and wisdom to be equivalent is called ‘seeing the Buddha-nature.’”[29][note 3]Regarding the practice of seated meditation, Shenhui did not teach that physical sitting was necessary.

"[32][note 4]In the early 10th century, the founder of the Fayan School commented on Shenhui's lineage: The record of that time was indeed excellent.

[3]Shenhui's own lineage, called the Heze school, probably died out around the time of the Great Anti-Buddhist Persecution in 845.

Mazu Daoyi, whose Hongzhou school became the hallmark of Zen, was an early and important adopter of the "sudden" approach.