Sōsan, also known as Sengcan, is traditionally remembered above all for a single, luminous work: the *Xinxin Ming* (often rendered as “Faith in Mind” or “Trust in Mind”). This compact poem, regarded as one of the earliest and most influential Zen texts, distills the heart of Chan/Zen into a series of terse, paradoxical verses. Rather than presenting a systematic philosophy, it offers a direct pointing to the nature of mind, inviting the reader to recognize an originally pure, undivided awareness. The text has been treasured and commented upon across Chinese and Japanese Zen traditions, precisely because it speaks to the experiential core of practice rather than to doctrine or speculation.

At the center of the *Xinxin Ming* stands the theme of non‑duality. Verses such as “The Great Way is not difficult for those who have no preferences” express the insight that clinging to opposites—love and hate, good and bad, right and wrong—obscures the Way that is otherwise ever‑present. When preferences fall away, reality appears “clear and undisguised,” no longer fractured by the mind’s habitual divisions. In this light, the poem’s teaching is not an abstract metaphysics, but a practical instruction: release the grip of dualistic judgment, and the unity of all phenomena quietly reveals itself.

Closely related is the poem’s emphasis on acceptance and non‑attachment. The verses repeatedly caution against seeking and avoiding, grasping and rejecting, or cherishing fixed opinions about truth. “Do not seek the truth; only cease to cherish opinions” encapsulates this stance, suggesting that awakening is not something to be acquired, but something that shines forth when conceptual elaboration relaxes. The unity of apparent opposites—being and non‑being, movement and stillness—is presented as the natural expression of a mind no longer caught in discrimination.

From this flows the teaching of effortless awareness. The *Xinxin Ming* encourages a natural, unforced approach to practice, where enlightenment is not the product of strain but the flowering of a mind that trusts its own depth. By “trust in mind,” the text points to confidence in the fundamental, undifferentiated mind that is already in accord with the Dharma. Talking and thinking about this mind only leads one astray; direct, non‑conceptual experience is held up as the true gateway. Historical records attribute few other specific teachings to Sōsan, yet this single poem has served as a touchstone for generations of practitioners, who find in it a concise yet profound map of the Zen path.