Chih-i illustrates that sūtra that is taken as the foundation for teaching (Chiao-pen) entails two aspects. On the one hand, it means that, based on single truth from the Word of the Buddha, there flow out countless speeches and teachings, such as the Common and Separate Teachings that can cause beings to attain the Path. On the other hand, based on the teaching of the Buddha, the bodhisattvas have made vast commentaries to explain the meanings in sūtras, which can also cause others to attain the Path. Sūtra that is taken as the foundation for practice (Hsin-pen) means that when one practices according to the teaching of the Buddha (whether it is Common or Separate Teaching), through these various Dharma-doors, one is able to attain the Ultimate Truth. Sūtra that is taken as the foundation for doctrine (I-pen) means that one doctrine can be derived from one sentence, and countless doctrines can be derived from countless sentences. It can also be the case that countless doctrines are derived from one sentence, and one doctrine is derived from countless sentences. Chih-i comments that summarizing these three aspects (teaching, practice and doctrine) in terms of the Dharma-door means that they are identical to the three ways to wisdom: hearing, thinking and cultivation (Wen Ssu Hsiu; Skt., śrutactābhāvanā), respectively. (Vol. 2, Page 391)