What is the relationship between the sacred and the profane, between the realm of the perfected saint and this imperfect world of everyday life, between the City of God and the City of Man, between heaven and earth, between this world and that world, between the Buddha and the ordinary ignorant man. In short, what is the nature of reality and existence? Is the pure realm of the sacred only an “ideal,” a “mythical” goal, separate from our ordinary lives and forever beyond our reach? If the perfect and ordinary are separate realms, how are they related, and how does one get “from here to there”? If they are the same, whence the suffering and painfully obvious imperfections of our mundane lives? These are questions which must be dealt with by any epistemology or religious philosophy, and by any person seeking an answer to the mysteries of life.

Nāgārjuna’s answer, which served as the basis for much of subsequent Mahāyāna Buddhist thought, is found in the Mūlamadhyamakakārikā [The Fundamental Wisdom of the Middle Way], most succinctly in chapter twenty-four, verses eight and nine:

8. All Buddhas depend on two truths
In order to preach the Dharma to sentient beings.
The first is the worldly mundane truth.
The second is the truth of supreme meaning.

9. If one is not able to know
The distinction between the two truths,
One cannot know the true meaning
Of the profound Buddha Dharma.

These verses are the most explicit formulation of the two truths, or twofold truth, theory of Mādhyamika philosophy. … Chih-i’s threefold truth concept is an extension of the traditional Mādhyamika theory of the two truths as explicitly taught in chapter twenty-four, verses eight and nine, of the Mūlamadhyamakakārikā. The direct literary inspiration for the formulation of the threefold truth concept is found in verse eighteen of the same chapter. …

This verse can and was interpreted as speaking of the identity of the two truths, emptiness (śūnyatā = paramārthasatya) and co-arising or conventional designation (pratītyasamutpāda = saṃvṛtisatya = prajn͂aptirupādāya), as the Middle Path (madhyamā). Kumārajīva’s Chinese translation of this verse, on which Chih-i relied completely, more clearly implies the understanding of the Middle Path as a third component in a single unity.

All things which arise through conditioned co-arising
I explain as emptiness.
Again, it is a conventional designation.
Again, it is the meaning of the Middle Path