Hui-san Hsien-i (Unifying the three and revealing the one) is the function related to the Subtlety of Practice. This is spoken of in terms of practice. Chih-i remarks that the purpose of the previous “opening the three” is for the convergence of various practices. This indicates that the Lotus Sūtra unifies the three aspects: person, dharma and practice (Jen Fa Hsing). All these three are integrated as bodhisattva practice on the path to Buddhahood, which refers to the convergence of the three and revelation of the one. (Vol. 2, Page 445)
The Profound Meaning of the Lotus Sutra: Tien-tai Philosophy of Buddhism