I think a fairly compelling case can be made that while Ch’an or Zen became the dominant Buddhist school during the second part of the T’ang Dynasty, the term “Ch’an” had not yet been turned into some kind of esoteric or metaphysical term. It just refered to Buddhist meditation or dhyana (P., jhana). Eventually, Ch’an or Zen would emphasize the realization of Buddha Mind.

Before the appearance of so-called “Ch’an Buddhism” in the T’ang there were masters who taught dhyana or meditation. The names of 21 dhyana (Ch’an/Zen) masters are listed in the biographical work, Kao-sêng-chuan completed in 519 by Hui-chiao which, by the way, does not include the name of Bodhidharma. It is over a hundred years later that we find the biographer Tao-hsüan listing 135 dhyana masters of which Bodhidharma and his close disciples are noted.

The early formation of Ch’an Buddhism does not rest on a particular school named “Ch’an School.” The prominent school was named “East Mountain Dharma Gate.” Before the creation of this school by Tao-hsin and Hung-jen there were probably only small groups of dhyana practitioners. One such group was Bodhidharma’s that was named the Lanka School because it used the Lankavatara Sutra as a vehicle of transmission.

It is the popularity of East Mountain Dharma Gate in the T’ang Dynasty that Zen as we know it begins to outline itself. It drew the attention of renowned literary figures and Empress Wu (684–704). It is through the East Mountain Dharma Gate that the Zen lineage begins with Bodhidharma, Hui-k’o, Seng-ts’an, etc.

The main spiritual emphasis of East Mountain was the “Mind to Mind transmission” (i-hsin ch’uan-hsin). When the student’s own purified mind resonated with the principle or absolute Mind, he was granted the Dharma. What we can gather from this is realization of Buddha Mind is the main feature of Ch’an Buddhism. Also, invoking the name of the Buddha to purify the mind was an important aspect of the practice of East Mountain.