A school of Chinese Buddhism, founded by Hui Ssu (515-577 CE) and Chih I (538-597 CE), which emphasizes the importance of the 'Lotus Sutra,' one of the integral scriptures of the Mahayana tradition. The name comes from Mount Tien in China where Hui Ssu lived and lectured. Essential features of T'ien T'ia include the concept of the threefold truth of empty, temporary, and middle, implying that all things are both distinct and part of a whole at the same time. An extension of this concept is the T'ien T'ia belief that all beings, though distinct, share the same Buddha nature and are therefore able to reach Buddhahood eventually. While T'ien T'ia acknowledges all other schools of Buddhism, it sees Buddhism as divided in 5 periods culminating in the 'Lotus Sutra' as the crown of the religion. T'ien T'ia declined in China after the persecutions of 845 CE but became popular in Korea and Japan as Tendai.