Sosan, also known as the Third Zen Patriarch, was a Chinese Zen teacher who made significant contributions to the development of Chinese Zen. His teachings and writings continue to influence Zen practitioners to this day.

One of Sosan's major contributions to Chinese Zen was his emphasis on the practice of meditation. He believed that meditation was the key to attaining enlightenment and encouraged his students to dedicate themselves to this practice. Sosan himself was known for his deep meditation practice and often used it as a means of teaching his students.

In addition to meditation, Sosan also emphasized the concept of "no-mind" or "non-duality." This idea is central to Zen philosophy and refers to the state of being free from all mental constructs and dualistic thinking. Sosan's teachings on no-mind helped his students to let go of attachments and to see the world in a more clear and direct way.

Sosan also played a crucial role in the development of koan practice in Chinese Zen. Koans are paradoxical or nonsensical statements or questions used to challenge the mind and break through conceptual thinking. Sosan is credited with creating the first collection of koans, known as the "Five Ranks," which has become a fundamental part of Zen training.

In addition to his teachings, Sosan also wrote several important texts that have had a lasting impact on Chinese Zen. His most famous work is the "Hsin Hsin Ming" or "Faith in Mind," a poem that is considered a masterpiece of Zen literature. This text emphasizes the importance of non-duality and the practice of meditation in attaining enlightenment.

Sosan's contributions to Chinese Zen also extended beyond his teachings and writings. He was known for his ability to transmit the dharma, or Buddhist teachings, through his presence and actions. Many of his students were said to have attained enlightenment simply by being in his presence and observing his way of being.

Overall, Sosan's emphasis on meditation, no-mind, koan practice, and his writings have had a profound impact on the development of Chinese Zen. His teachings continue to be studied and practiced by Zen students around the world, making him a significant figure in the history of Zen Buddhism.