[In Chih-i’s view,] the Lotus Sūtra as the perfect teaching is justified as it contains the subtlety of the twelve types of scripture. The following is Chih-i’s explanation of why the twelve types of scripture contained in the Lotus Sūtra are considered to be subtle.

1. llsiu-to-luo (Sūtra) as the prose portion is called the direct speech, and contains the subtlety of the Lotus Sūtra, for this prose form of sūtra directly expounds the Middle Way as the knowledge of the Buddha.
2. Chih-yeh (Geya) as the verse form is subtle, for it is the repetition of the prose portion that sūtra represents, and concerns the doctrine of the Middle way.
3. Chia-t ‘o (Gāthā) as the independent verse is subtle. This is because, the verse portion in the Lotus Sūtra regarding the dragon girl who attained Buddhahood in one instant is independent, i.e., it is not the reiteration of the prose portion. This portion in verse form describes the dragon daughter who attains enlightenment in one second, which proves that the independent verse portion gāthā is subtle.
4. Pen-shih (Itivṛttaka) that concerns the past lives of the disciples of the Buddha is subtle, whereas twenty thousand Buddhas do not teach anything else but the unsurpassed Path.
5. Pen-sheng (Jātaka) that concerns the previous lives of the Buddha is subtle, for it is the story about the material body of the Buddha being born as a prince, and the dharmakāya being manifested as a bodhisattva.
6. Yin-yüan (Nidāna) as the historical narratives is subtle, for the Buddha repeatedly proclaims the Greater Vehicle to beings, regardless of whether they are of the Lesser Vehicle, or of the Human and Heavenly Vehicle.
7. Wei-ts ‘eng-yu (Adbhutadharma) that concerns rare events is subtle, for the auspicious signs the Buddha manifests, such as heavenly flowers raining down, the trembling of the earth, the ray of light exerting from between the Buddha’s eyebrows, and transforming land three times, are inconceivable.
8. P’i-yü (Avadāna) that concerns allegories is subtle, for the title of the Lotus Sūtra uses the word Fa (dharma) as a metaphor for nothing else but the disclosure of the Three Vehicles (śrāvaka, pratyekabuddha and bodhisattva) and the revelation of the One Buddha-vehicle.
9. Lun-i (Upadeśa) that concerns the discussions of doctrine is subtle. This is evidenced by the interaction between the dragon girl and the bodhisattva Wisdom Accumulation. The bodhisattva Wisdom Accumulation, being attached to the Separate Teaching and being suspicious of the Perfect Teaching, did not believe that the dragon girl can instantly attain Buddhahood. The dragon girl, after declaring that the Buddha can testify and see the possibility of her attainment of Buddhahood in one second, offered the Buddha a precious gem. Chih-i explains that the gem represents perfection, which is to answer the disciple of the Separate Teaching by means of the Perfect Teaching.
10. Wu-wen Tzu-shuo (Udāna) that concerns the self-generated statement of the Buddha is subtle, for it is mentioned in the Lotus Sūtra that the Buddha speaks by himself without being questioned in order to praise the Buddha-wisdom.
11. Shou-chi (Vyākaraṇa) that concerns prophecies of the Buddha is subtle, for it is mentioned in the Lotus Sūtra that the Buddha prophesizes listeners’ future Buddhahood. They will be able to peacefully abide in the ultimate wisdom and be revered by humans and heavenly beings.
12. Fang-kuang (Vaipulya) that means correct and universal is indicated by the Buddha-vehicle and the Buddha-wisdom the Lotus Sūtra upholds, for the Buddha-vehicle is superior and universal, and the Buddha-wisdom is profound and abstruse.

The above is the description of the Subtlety of Expounding the Dharma. This subtlety represents the teaching of the Buddha in terms of the twelve types of scripture. In Chih-i’s view, all divisions of Buddhism whether of Śrāvakayāna or Mahāyāna are the “Word of the Buddha.” It is due to different circumstances and different capacities of beings that the teaching of the Buddha varies in order to suit specific situations. Since the Buddha’s proclamation of the dharma is spoken of in terms of the twelve types of scripture, the twelve types of scripture incorporate all teachings of the Buddha.

Yet, how do the twelve types of scripture fit into Chih-i’s system of classification in terms of the Four Teachings (Tripiṭaka, Common, Separate and Perfect), in which the Perfect Teaching is exclusively subtle? First, it must be determined whether the teaching (Neng-ch’üan) and the doctrine (Suo-ch’üan) of each of the Four Teachings are coarse or subtle. The Tripiṭaka Teaching is coarse in terms of both the teaching and doctrine; the Common Teaching is coarse in terms of doctrine, and subtle in terms of teaching; the Separate Teaching is coarse in terms of teaching, and subtle in terms of doctrine; and the Perfect Teaching is subtle in terms of both teaching and doctrine. Therefore, the Perfect Teaching is subtle only. Second, various sūtras must be examined, that are expounded in the five periods of the Buddha’s teaching, from which the Lotus Sūtra is said to contain one Perfect Teaching only. Third, since the Lotus Sūtra represents the Perfect Teaching, the former is perfect. Such a perfect feature is reflected by the subtlety of the twenty types of scripture that are contained in the Lotus Sūtra. (Page 287-289)