Tradition places Chih-i as the third in the line of patriarchs in the T'ien-t'ai school, but in fact he founded the school and furnished most of its distinctive teachings himself, including (1) the T'ien-t'ai method of organizing and classifying scriptures and teachings known as p'an-chiao which gave the Lotus Sūtra the honoured place as the supreme scripture (see P'an-chiao); (2) the Three Truths that overcame the disconnection between the traditional Two Truths of Madhyamaka teaching; (3) the idea that the transcendent principle (Chinese, li) and phenomenal reality (Chinese, shih) mutually interpenetrate without obstruction; (4) and the idea of One Mind or absolute mind that underlies all of reality, in both its pure and defiled aspects. He was also renowned as a meditation master, and wrote a massive treatise on the methods and rationales of meditation, epitomized in the term chih-kuan, or ‘calming and contemplation’.
Chih-i was born into a family in south China with aristocratic connections, but realized the transitoriness of life at a young age after witnessing troops destroy a library. He became a monk, and studied with the renowned meditation master from north China Hui-ssu (515-77), later recognized as the second patriarch of T'ien-t'ai. After a stay in Chin-ling (modern Nanking), he went to Mt. T'ien-t'ai on the eastern seaboard in Chekiang province, and remained there for most of the rest of his life; it is from his residence and work there that the school derived its name. An early visionary experience aroused his faith (śraddhā) in the supremacy of the Lotus Sūtra, and during his career he wrote two commentaries on it, one a general survey of its meaning, the other a line-by-line exegesis. When China was reunited by the Sui dynasty in 581, his family's connections brought him to the attention of the court, where he was invited to preach and was duly honoured. The resulting patronage allowed him to buy the fishing rights along the coastline adjacent to Mt. T'ien-t'ai and to obtain an imperial ban on fishing in the area that remained in effect for at least two centuries.