Chu-i Hsien-i (Abiding in the one and revealing the one) is the function related to the Subtlety of the Threefold Track. This is spoken of in terms of the original intention of the Buddha. Chih-i emphasizes that the Buddha’s intention is to apply the ultimate knowledge to transform living beings. Therefore, the Buddha always abides in the One Buddha-vehicle, and expounds this One Vehicle to teach and transform living beings. (Vol. 2, Page 445)