Sosan, known in Chinese as Sengcan, stands in the Chan tradition as a crucial early figure whose significance lies less in dramatic biography and more in the shaping of Zen’s inner spirit. As the third patriarch in the traditional lineage from Bodhidharma through Huike to Daoxin, he serves as a vital link that helped solidify the idea of an unbroken, mind-to-mind transmission. This continuity of transmission became a defining feature of Chan identity, grounding its authority in direct realization rather than in scriptural or institutional validation. Through this role, Sosan contributed to the self-understanding of Chinese Zen as a living stream of awakened mind.

His name is most closely associated with the *Xinxin Ming* (“Inscription on Trust in Mind” or “Faith in Mind”), one of the earliest and most influential Zen texts. Chan tradition credits this poem to Sosan, and regardless of modern scholarly debates, it clearly embodies the doctrinal atmosphere attributed to him. The text articulates a radical non-dualism: the transcendence of opposites, the futility of clinging to preferences, and the dissolution of the split between subject and object, samsara and nirvana, purity and impurity. It teaches that true understanding arises when discriminating thought is relinquished and the fundamental mind is trusted rather than grasped conceptually.

The teachings associated with Sosan place strong emphasis on “no-mind” (wuxin), pointing to a mind free from fixation and fabrication. In this vision, awakening is not the acquisition of something new but the recognition of an already-complete, ungraspable nature of mind. Such an outlook integrates the Buddhist insight into emptiness with a more immediate and intuitive style that resonated deeply with Chinese sensibilities. The result is a form of practice in which emptiness is not an abstract doctrine but the natural, everyday functioning of mind when it is no longer divided against itself.

The *Xinxin Ming* also helped shape the literary and practical ethos of later Chan. Its aphoristic, paradoxical, and poetic expression became a model for how profound insight could be conveyed in a compact, evocative form, blending philosophical depth with direct practical instruction. Many themes later prominent in the more contemplative currents of Chan—such as non-striving, “just thusness,” and quiet confidence in original mind—are anticipated in the teachings attributed to Sosan. Through this combination of lineage, doctrine, and literary expression, Sosan’s legacy helped provide Chinese Zen with both a theoretical foundation and a distinctive inner tone that continued to echo through subsequent generations.