According to Tiāntái Zhiyi, the characteristic teaching of the Lotus Sūtra is “opening and merging,” in Japanese kai-e. This means unifying all the past provisional teachings into the one true teaching. Tiāntái classified 28 chapters of the Lotus Sūtra into two parts: the first 14 chapters as Trace Gate, in Japanese shakumon, and the last 14 chapters as Original Gate, in Japanese honmon. The Trace Gate takes the form of preaching by a “provisional Buddha,” the historical Śākyamuni Buddha depicted as having first awakened during his lifetime in India. The Original Gate takes the form of preaching by the Buddha who has discarded this provisional status and revealed his true identity as the Buddha who attained awakening in the remotest past. in Japanese kuon-jitsujō, as revealed in Chapter 16 of the Lotus Sūtra.

Accordingly, in the period of the Lotus Sūtra, the past provisional Buddha and the provisional teachings were all unified to the pure Eternal Buddha and his true teaching.