Chih-i reiterates that although there are different teachings in accordance with different abilities of beings, the Ultimate Truth as substance is the same. He explains that the Buddha teaches four different Dharma-doors in accordance with four kinds of faculties of beings. Different teachings of the Buddha designate names different. Separate functions of the teaching designate meanings also different. However, as one’s final realization of the principle is not different, the underlying substance is the same. (Vol. 2, Page 416)