With regard to sūtra that means foundation for the dharma (Han Fa-pen), Chih-i explains that the dharma is inexpressible, but for the sake of teaching sentient beings, the Buddha expounds the dharma by means of the Four Siddhāntas. To be associated with the three perspectives, the Worldly Siddhānta is taken as the foundation for teaching; the Siddhānta for Each Person and the Siddhānta of Counteraction are taken as the foundation for practice; the Siddhānta of Supreme Truth is taken as the foundation for doctrine. (Vol. 2, Page 390)