This paper examines the transmission of the Shōbōgenzō 正法眼蔵 （Treasury of the True Dharma Eye） in the early Sōtō Zen School, with a focus on Keizan Jōkin 瑩山紹瑾 （1264-1325）. It has been assumed that the text had been passed down following relationships of Dharma transmission, from Dōgen 道元 to Ejō 懐奘 （1198-1280）, to Tettsū Gikai 徹通義介 （1219-1309）, to Keizan. However, based on what can be gleaned from extant documents and their postscripts, it is conjectured that Gikai did not participate in the transcription of the Shōbōgenzō.
I begin by examining the process by which Gikai could have acquired the Shōbōgenzō without participating in its transcription. Gikai was asked to manage the Buddhist scriptures of Hajaku-ji temple 波着寺 by Ekan 懐鑑 （?-1251?）, as his dying wish. There is a postscript stating that the Shōbōgenzō was transcribed at Hajaku-ji in 1273. Consequently, Hajaku-ji held a copy of the Shōbōgenzō on which this transcription was based, and Gikai may have transmitted this to Keizan.
In addition, I examine the possibility that Keizan was introduced to the text by someone other than Gikai. The most plausible candidate for this is Gien 義演 （?-1314）. In 1292, Gien taught Keizan the Busso shōden bosatsukai sahō 仏祖正伝菩薩戒作法 （Instructions on the Bodhisattva Precepts correctly transmitted by the Buddhas and ancestors）. Therefore, it is possible that he transmitted the Shōbōgenzō to Keizan at the same time.
However, the postscript to the Shōbōgenzō said to have been transcribed at Hajaku-ji does not mention the name of the transcriber. Thus, it is speculated that the transcription of the Shōbōgenzō may have been performed not by a single person, but by multiple persons instead. Accepting this premise poses the need to examine a wider range of candidates, including Gikai and Keizan themselves, among others.
The above hypotheses still leave many problems to be solved. Hence, it is difficult to formulate a theory at present, and further study is required.
