Yaoshan Weiyan

Yaoshan Weiyan (藥山惟儼, 751–834) is recorded in the Tang biographical compilations and in the *Jǐngdé Chuándēng Lù* as the heir of Shitou Xiqian who also spent time studying with Mazu Daoyi — one of the few Tang masters whose biographies place them at both of the great Hongzhou and Qingyuan streams^[1]. After leaving Mazu's community he settled on Mount Yao (Yaoshan, in modern Hunan), where his sparse, probing style and his refusal to court official patronage made the mountain a magnet for serious practitioners^[2].

The most consequential of his exchanges for later Zen is preserved in the *Jǐngdé Chuándēng Lù*: a monk asked what he was thinking as he sat so still, and Yaoshan answered, "I think of not-thinking" (思量箇不思量底); pressed on how one thinks of not-thinking, he replied, "*Hishiryō* — beyond thinking" (非思量)^[3]. Dōgen quotes this dialogue almost verbatim at the climax of the *Fukan Zazengi* and again in the *Zazenshin*, anchoring the Sōtō understanding of *shikantaza* in Yaoshan's formula^[4]. Yaoshan's principal heirs Yunyan Tansheng and Daowu Yuanzhi carried his line forward; through Yunyan it reached Dongshan Liangjie and became the Caodong / Sōtō school proper.