[T]he Buddhist world in South and North China during fifth and six centuries was divided by its focus on either the doctrinal aspect or practical aspect. Chih-i’s elaboration of the first three Subtleties (Objects, Knowledge and Practice) resolves the discrepancy between Southern and Northern branches by laying equal importance of both doctrinal and practical aspects.

1. The Subtlety of Objects emphasizes the importance of the doctrinal aspect concerning truth. Without truth, liberation is not possible, since one’s attainment of liberation is based on one’s realization of truth.
2. The Subtlety of Knowledge connects these aspects with each other. On the one hand, because of knowledge, one is able to penetrate the doctrine of truth. On the other hand, from Chih-i’s elaboration of knowledge (as we see how the twenty kinds of knowledge are derived from various types of practice),29 knowledge is obviously related to the practical aspect: without practice, knowledge cannot be obtained.
3. The Subtlety of Practice emphasizes the significance of the practical aspect in obtaining knowledge and penetrating truth. Therefore, these three subtleties embrace all aspects of Buddhism, for all aspects of Buddhism are concerned with doctrine and practice. (Vol. 2, Page 465)

Chih-i’s system of classification conveys that the Tripitaka Teaching can be regarded as representing purely the Śrāvakayāna, and the Separate Teaching purely the Mahāyāna. The Common Teaching is the bridge connecting these two teachings, as it contains both elements of Śrāvakayāna and Mahāyāna. Its Śrāvakayāna element is reflected by its goal of reaching emptiness like that of Śrāvakayāna, and its Mahāyāna element is reflected by its way of perceiving emptiness. Different from the disciples of the Tripiṭaka Teaching who reach emptiness by extinguishing existence, i.e., analyzing and disintegrating dharmas until nothing is left, the disciples of the Common Teaching perceive emptiness by embodying dharmas, i.e., existence is illusory and thus empty.28 Finally, the Perfect Teaching transcends the difference of the former three teachings, and unifies Śrāvakayāna and Mahāyāna with its doctrine of the Ultimate Truth of Buddhahood. That is, all different types of the teaching are the necessary progressions leading to the final teaching of Buddhahood. (Vol. 2, Page 465)

What we can determine from Chih-i ‘s interpretation of the Lotus Sūtra in the Hsüan-i is that his interpretation is his approach to establish his system of understanding Buddhism, which reflects his perfect harmonization philosophy. Based on his perfect harmonization philosophy, Chih-i manages to comprehensively and coherently portray various theories of different Buddhist schools so that all divisions, aspects, learnings, and theories of Buddhism that appear to be incoherent come to terms with each other as a whole. This is reflected in Chih-i’s presentation of the Buddha’s teaching in which two divisions of Buddhism, the Śrāvakayāna and Mahāyāna, are complimentary to each other rather than contradictory to each other. According to Chih-i, the Buddha’s teaching centers on enlightenment for oneself and for others. Enlightenment for oneself can be generally considered as the goal of Śrāvakayāna Buddhism, and enlightening others as the goal of Mahāyāna Buddhism. As these two divisions appeared to be disconnected before Chih-i ‘s time, they have been unified as a whole in Chih-i’s theory.

The unification of Śrāvakayāna and Mahāyāna is based on Chih-i’s theory of the essential teaching of the Buddha, concerning the cause and effect of Buddhahood. The cause of Buddhahood refers to the Buddha’s practice to attain enlightenment for himself and is embodied by Śrāvakayāna Buddhism; and the effect of Buddhahood refers to the Buddha’s enlightenment that results in his teaching and transformation of sentient beings in order to enlighten them and is embodied by Mahāyāna Buddhism. With this theory of the cause and effect of Buddhahood, the differences between these two divisions of Buddhism are resolved, as each of them represents one aspect of Buddhahood. Since the cause and effect of Buddhahood is the vital force that unifies different aspects of Buddhism, this essential teaching is what underlies Chih-i’s system of understanding Buddhism, and is laid out in the Fa-hua Hsüan-i. (Vol. 2, Page 462)

Chih-i quotes passages in the “Chapter On Faith and Understanding” in the Lotus Sūtra concerning the parable about the rich father and his poor son, in order to analogize the Buddha’s teaching in terms of five periods.

1. The passage about the rich father dispatching an attendant to follow his poor son in order to bring him back, and the poor son being terrified, analogizes the Avataṃsaka teaching in the first period that belongs to the Sudden teaching. Chih-i asserts that this is as if from the cow, one extracts fresh milk.
2. The passage about the rich father wishing to entice his son, putting his son to hard work, while disguising himself in dirty clothes as an expedient means in order to approach his son and to keep him at work clearing away dung for twenty years, analogizes the Tripitaka Teaching in the second period that caters to the śrāvakas. Chih-i articulates that this is like from fresh milk, one extracts cream, and from the twelve types of scripture, sūtras are produced.
3. The passage about the poor son at the end of this time gaining confidence in himself, and coming and going without anxiety, though he was lodged in the same place as before, analogizes the Vaipulya teaching in the third period. Chih-i declares that this is like from cream, one extracts curdled milk, and from sūtras, the Vaipulya Sūtras are produced. In this period, the Buddha begins to expound the Greater Vehicle, though the śrāvakas still dwell in the teaching of the Lesser Vehicle.
4. The passage about the rich father telling his son about his treasure houses and his son is conferred to be in charge of the multitude of things, and yet his son had no craving for so much as a single meal, and continued to live as before in the same place, analogizes the Prajn͂āpāramitā teaching in the fourth period. This is like from curdled milk, one extracts butter, and from the Vaipulya Sūtras, the Prajn͂āpāramitāsūtra is produced. Chih-i remarks that the Prajn͂āpāramitā teaching concerns wisdom, and wisdom is treasure.
5. The passage about the rich father declaring the father and son relationship to the multitude, and the poor son being rejoiced and greatly bequeathing all riches of his father which he had never had before, analogizes the Saddharmapuṇḍarīka-Mahāparinirvāṇa teaching in the fifth period. Chih-i articulates that this is like from butter, one extracts ghee, and from the Prajn͂āpāramitāsūtra, the Nirvāṇasūtra is produced. (Vol. 2, Page 456-457)

In order to prove his classification of the sequence of the Buddha’s teaching, Chih-i quotes the passages from the “Chapter On Expedient Means” in the Lotus Sūtra, such as “When I first sat at the bodhimaṇḍa, whether observing or practicing, throughout three weeks, contemplating on such a thing: ‘The knowledge and wisdom I have gained is the uttermost subtle thing. Living beings with their dull faculties … . How can they be saved? I had rather not teach the dharma but enter rapidly into nirvāṇa. When I think back on the Buddhas of the past, on the power of the expedient means put into practice by them, I know that in the Path I have now gained, I too must teach the Three Vehicles.” Chih-i explains that the phrase “when I first sat at the bodhimaṇḍa” expresses the teaching that is characterized by Sudden. In Chih-i’s theory, at the beginning of the teaching career upon the Buddha’s enlightenment under the bodhi tree, the Buddha teaches the Greater Vehicle to the bodhisattvas, and this teaching belongs to the Sudden teaching. Moreover, the assertion of the Buddha that he must teach the Three Vehicles proves that after the initial teaching of the Sudden, the Buddha’s teaching of the Three Vehicles can be characterized as the Gradual teaching. (Vol. 2, Page 456)

In this first part, Chih-i addresses that the teaching of the Lotus Sūtra is superior to the teachings in other sūtras. He states that various types of the teaching of the Buddha are equally beneficial to various living beings, from the viewpoint that each of them suits certain capabilities of beings. Nevertheless, respecting the methods of the teaching, there exist differences among them. The teachings of other sūtras do not express the real intention of the Buddha, as they are the product of suiting the understandings of listeners. The teaching of the Lotus Sūtra, with the true knowledge of the Buddha, directly conveys the real intention of the Buddha, and leads all beings to attain Buddhahood. Therefore, the teaching of the Lotus Sūtra is superior to the teachings of other sūtras. (Vol. 2, Page 453-454)