In the sixth century, the Chinese monk Zhiyi (538-597) established a teaching center on Mt. Tiantai. He was later known as the Great Master Tiantai, founder of the school of the same name. Zhiyi was a great scholar and meditator who wanted to systematize all the seemingly contradictory teachings that had been translated into Chinese. To do this, he classified the Buddha’s teachings into five flavors and eight categories of teaching. As a practitioner, as well as a scholar, he put equal emphasis on meditation practice and doctrine in order to create a balanced system whereby doctrine would inform practice and practice would actualize doctrine. The concept of the “three thousand realms in a single thought-moment” … was part of his explanation of the sudden and perfect method of tranquility and insight meditation. He also spoke of awakening in terms of realizing the unity of the threefold truth of emptiness, provisional existence, and the Middle Way in order to clarify the true meaning of the teachings of the Perfection of Wisdom sūtras and Nāgārjuna’s (second-third century) teachings regarding emptiness, causality, and the Middle Way. He derived the unity of the threefold truth from a line in Nāgārjuna’s major work, Verses on the Middle Way:

“Whatever is dependently co-arisen
That is explained to be emptiness.
That, being a dependent designation,
Is itself the middle way.” (Garfield, p. 304)

Zhiyi taught that the threefold truth could be realized through a “threefold contemplation” cutting through the “three categories of delusion” and giving rise to the “three kinds of knowledge.” Ultimately, Zhiyi taught that the three truths of the threefold truth are simply different aspects of the one true nature of reality that can be realized in a single moment of insight.