T’ien-t’ai school ［天台宗］ (PY Tiantaizong; Tendai-shū): A major school of Buddhism founded by T’ien-t’ai (538–597), also known as Chih-i, in China. The school emphasizes two principal disciplines: doctrinal studies and meditative practices. Concerning the former, it adopted a system of classification that organizes all the Buddhist sutras into five periods and eight teachings to clarify their relative position, and based itself on the Lotus Sutra. It also teaches the doctrine of three thousand realms in a single moment of life, the unification of the three truths, the six stages of practice, and others.
Concerning meditative practices, the school maintains that enlightenment is achieved by meditation or observation of one’s mind; through such practices one aims to perceive the three truths within one’s own life. This practice, called “the threefold contemplation in a single mind,” is said to have been established by Hui-wen based on Nāgārjuna’s works The Treatise on the Great Perfection of Wisdom and The Treatise on the Middle Way. Hui-wen transmitted it to Nan-yüeh, who in turn taught it to T’ien-t’ai. T’ien-t’ai refuted the three schools located to the south of the Yangtze River and the seven schools located to the north, all of which believed in the supremacy of either the Flower Garland Sutra or the Nirvana Sutra. He asserted that Shakyamuni’s ultimate teaching is to be found in the Lotus Sutra. His lectures on the Lotus Sutra were recorded and compiled by his immediate successor Chang-an, and they became known as the three major writings of the T’ien-t’ai school: The Profound Meaning of the Lotus Sutra, The Words and Phrases of the Lotus Sutra, and Great Concentration and Insight.
Because T’ien-t’ai established and systematized both the doctrine and practice of the school, he is regarded as its founder. T’ien-t’ai’s teaching was transmitted successively to Chang-an, Chih-wei, Hui-wei, Hsüan-lang, Miao-lo, and others. Miao-lo wrote commentaries on the three major writings and is credited with the restoration of the school. In 804 Miao-lo’s disciples Tao-sui and Hsing-man taught the T’ien-t’ai principles to Dengyō (also known as Saichō), who had come from Japan to further his studies. Dengyō later founded the Japanese Tendai school (“Tendai” is the Japanese reading of the Chinese T’ien-t’ai). The T’ien-t’ai school declined in China amid the suppression of Buddhism by Emperor Wu-tsung in 845 and the warfare that broke out toward the end of the T’ang dynasty (618–907); many of its texts were lost. The beginning of the Sung dynasty (960–1279) saw a revival of the school during the time of its eleventh patriarch, Ch’ing-sung. Later, however, it divided into two branches, one from the lineage of I-chi and the other from that of Chih-yin. Ichi collected the texts of the T’ien-t’ai school and devoted himself to its restoration. I-chi was succeeded by I-t’ung and then by Chih-li. Chih-li’s group called itself the Mountain (Chin Shan-chia; Sange) school, emphasizing its conviction that it was within the true lineage of Mount T’ien-t’ai, the original base of the T’ien-t’ai school. They called the other branch the Outside-the-Mountain (Shan-wai; Sangai) school, suggesting deviation from the true lineage.
Along with the wane of Chinese Buddhism in general due to foreign invasions at the end of the Sung dynasty, the T’ien-t’ai school also gradually declined. The texts of the school were first brought to Japan by the Chinese priest Chien-chen ( Ganjin) in the mid-eighth century. It was Dengyō, however, who studied them in earnest, went to China to learn the depths of T’ien-t’ai principles, and established the Tendai school in his homeland based upon those teachings.