The studies conducted over so many centuries made possible a deeper understanding of the Lotus Sutra, and methodological standards for its interpretation were established. One example is called Kamon. It is a classification of the twenty-eight chapters into several sets for a systematic explanation of their meaning.
The major Kamon is the “Three Parts of Each of the Two Divisions of the Lotus Sutra” which was established by Great Master Chih-i. Most commentators since his time have accepted his guidelines. …
[T]he “Three Parts of Each of the Two Divisions of the Lotus Sutra” refers to the division of the Sutra into two main sections: the first half, consisting of Chapters One through Fourteen, and the second half, consisting of Chapters Fifteen through Twenty-eight. Kamon gives a detailed explanation of the reason for this division. The first half is named Shakumon, literally “imprinted gate.” Its main purpose is to teach how “hearers” and Pratyekabuddhas can attain Buddhahood in the One Vehicle. The second half is called Hommon, which means “Primal Gate” or “Primal Mystery.” This part reveals Sakyamuni to be the infinite, absolute Buddha, the Buddha who attained enlightenment in the remotest past but still leads living beings in the present. These two points are considered the fundamental ideas of the Lotus Sutra.
Introduction to the Lotus Sutra