Sima Chengzhen

Sima Chengzhen (d. 735) was a Daoist priest and expert on Confucian classics in the Tang Dynasty. He lived as a hermit in the Tiantai Mountains, and called himself "Tiantai Baiyunzi."

Sima believed that qi (vital force or energy) was the source of the fetus, and the source of the physical body. He also believed that Dao had great energy and could gradually change a person's body and soul; those who could keep their physical bodies in line with Dao and integrated with spirit could be deemed as immortals. He asserted that the unity of physical body and spirit could help human beings transcend life and death. This theory laid a solid foundation for his philosophy of comprehensively cultivating physical and spiritual health.

司馬承禎

司馬承禎，唐朝道士，深諳儒典，隱居在天臺山，自稱“天臺白云子”。他認為，“夫氣者，胎之元也，形之本也”，“道有深力，徐易形神；形隨道通，與神合一，謂之神人”，意指只有形神合一，才能超越生死境界。這種聚氣成形，形神合一、超越生死境界的生命元氣本體論，正是司馬承禎建構“性命雙修”心性論的哲學理論基礎。