The idea of original enlightenment as expounded in the Awakening of Faith in the Mahayana (Dacheng qixinlun) differs in logic from the thought of Original Enlightenment that spread in Japan's Middle ages. The fundamental principle of the Awakening of Faith in the Mahayana is the principle of the Matrix of the Tathagata. On the contrary, the fundamental principle of the Tiantai idea of the Original Enlightenment is based on Nagarjuna's idea of non-substantiality.
In the Tiantai idea of original enlightenment from the Four Teachings-Tripitaka, Connecting, Specific, and Perfect Teachings-one is expounded the concept of the “four-fold rise and fall” which comprises the pre-Lotus Sutra, Theoretical Teaching of the Lotus Sutra, the Essential Teaching of the Lotus Sutra, and the Observation of the Mind. The purpose of this concept is to reveal the absolute theory of complete fusion of the truth and perfect equality of the Law based on the idea of non-substantiality. According to this concept, the pre-Lotus Sutra teachings are those of discrimination. The purpose of the Theoretical Teaching of the Lotus Sutra is to reveal theoretical absolute equality. The purpose of the Essential Teaching of the Lotus Sutra is to teach true absolute equality. The purpose of the teaching in the Lotus Sutra's Observation of the Mind is to reveal that the self-manifestation of absolute equality transcends the comparison of different natures.