This is the last part in elaborating the Four Siddhāntas. By stressing that the Four Siddhāntas are expressed in the Lotus Sūtra, Chih-i legitimizes his own view concerning the Lotus Sūtra as the ultimate teaching of the Buddha embracing all types of the teaching. The passage is quoted by Chih-i from the “Chapter on Expedient Means” (Fang-pien-p’in) in order to prove that the meaning of the Four Siddhāntas can be drawn from it:

“[The Buddha] understands all actions of living beings, what they think in their deep minds, their habitual tendencies [they carry] from the past, their desires, their nature, the power of their exertions, and whether their faculties are acute or dull. [The Buddha] employs various causes and conditions, similes, parables, and other words and phrases, adapting whatever means that are suitable to expound his teaching.”

This passage is interpreted by Chih-i as:

” ‘Desire’ is the [mundane] pleasure and desire, which indicates the Worldly Siddhānta. ‘Nature’ refers to the nature of knowledge and wisdom, which indicates the Siddhānta for Each Person. The ‘power of exertions’ refers to the destruction of evil, which indicates the Siddhānta of Counteraction. ‘Acute or dull faculties’ refers to different realizations attained by two people [with either acute or dull faculties], which indicates the Siddhānta of the Supreme Truth.”
Chih-i associates the phrases “their desires” with the Worldly Siddhānta (for the teaching suits the desire of living beings), “their nature” with the Siddhānta for Each Person (for nature means the nature of knowledge and wisdom which denotes the wholesomeness this teaching is intended to produce), “the power of their exertions” with the Siddhānta of Counteraction (for power is meant to destroy evil, which is the intended result of this teaching), and “whether their faculties are acute or dull” with the Siddhānta of the Supreme Truth (for the teaching aims at enlightening living beings of different capacities).

Through such an interpretation that reveals the meaning of the Four Siddhāntas implied in the Lotus Sūtra, the validity of the Lotus Teaching is confirmed.