[T]he meaning of the subtlety (Miao-i) is concluded by Chih-i as signifying the single reality of the teaching of the Buddha. This is to say that the teaching of the Buddha concerns the Ultimate Truth of Oneness:

1. Oneness of principle (Li-i) in terms of the Ten Dharma-realms (that the truth the Buddha intends to convey is one).
2. Oneness of teaching (Chiao-i) in terms of the five flavors (that all teachings of the Buddha contain the same goal of leading living beings to attain Buddhahood).
3. Oneness of practice (Hsing-i) in terms of contemplating mind (that all practices aim at attaining truth).
4. Oneness of person (Jen-i) in terms of the six identities that various transformations of the Buddha (manifested in different levels of attainment) are ultimately one the eternal Buddha, and that all living beings will be able to attain Buddhahood. (Vol. 2, Page 27)