In so doing, Tiantai removed the duality of this world versus nirvana, which had been characteristic of Indian thought.
In teaching the idea that Buddha-nature is inherent in all people, Tiantai it does away with the caste-like hierarchies of enlightenment that were more characteristic of early Theravada.
By saying that reality was “subtle” (both substantial and empty at the same time), Tiantai enabled Chinese Buddhists to look beyond Indian sutras to understand the nature of reality (i.e. it could only be understood from direct interaction with the world, more than the study of scriptural philosophy).