At eighteen, Hongzhi Zhengjue went to study with Kumu Facheng, a teacher of the Caodong line of Chan whose sitting was so still that his name, Kumu, means "dry wood". The young monk, born in Xizhou in today's Shanxi, had left home at eleven. He kept Kumu's way of sitting, upright and unmoving, for the rest of his life, and he built a teaching on it. It was called mozhao, silent illumination: sitting without an object and without a goal. Thinking settles, and the mind's own clarity shows itself, because awakening is already present in everyone and needs to be lived out rather than acquired. His short "Inscription on Silent Illumination" insists that the two halves need each other: stillness without illumination turns murky, and illumination without stillness turns aggressive.
The line he joined had nearly died out a few generations earlier. Both Kumu and Hongzhi's next teacher, Danxia Zichun, were disciples of Furong Daokai, who had revived the Caodong school and set strict rules for its monasteries. Furong refused honours from the emperor as unfit for a monk and was exiled, though pardoned the next year; Hongzhi wrote a poem in his praise. Hongzhi received Danxia's seal of transmission before Danxia died in 1119, and he also spent time with Yuanwu Keqin, the Linji master who compiled the Blue Cliff Record. Morten Schlütter, a historian of Song Chan, has argued that silent illumination itself was a product of this revived Caodong line in the early twelfth century.
In 1129 Hongzhi became abbot of the Jingde monastery on Mount Tiantong, near the coast of today's Zhejiang. The monastery was small and in disrepair; under him it was rebuilt to hold twelve hundred monks, and he refused every invitation to leave. These were years of war after the Jin conquest of the north, and of hunger. He ate nothing after noon, and more than once he gave the monastery's food to the villages around it. Dōgen, the founder of Japanese Sōtō Zen, later told how a steward begged Hongzhi to send away the hundreds of monks the stores could not feed, and was told that each of them had his own mouth and it was not the steward's concern.
Dahui Zonggao, the leading master of the rival Linji line, campaigned against what he called the heretical Chan of silent illumination, whose teachers, he said, told troubled officials to make their minds cold ash and dead wood. Dahui told them instead to hold one phrase from an old kōan with all their doubt. Later partisans of both schools turned this into a feud between the two men, and historians still dispute whether Dahui meant Hongzhi at all. They were colleagues. Hongzhi never answered the criticism, sent food to Dahui's monastery when it ran short, and recommended him as abbot of another great monastery. In the autumn of 1157 he came down the mountain for the first time in nearly thirty years to thank his patrons. Back on the mountain, before he died, he wrote asking Dahui to take charge of Tiantong.
His disciples gathered his sermons, verses and instructions into the nine volumes of the Hongzhi chanshi guanglu, his "extensive record", and his hundred verses on old kōans became the core of the Book of Serenity, printed in 1224. Three years later Dōgen received transmission at the same Tiantong monastery. Dōgen quotes Hongzhi more than any other Chan master.