According to the veiled worldly or relative truth, things are real. According to the ultimate truth, they are unreal because they are non-substantial. Reality is perceived in terms of these two truths. Since the ultimate truth cannot be obtained independently of the relative truth, and liberation is not obtained without the ultimate truth, the real can only be attained through the unreal.
If the relative truth is unreal and false, then why bother with it? Why not go directly to the ultimate truth? This is the mistake people like Nichiren made, to seize onto the ultimate truth as if it were something real, but the ultimate truth is that everything is unreal. Everything is false, and so ultimately there is nothing that can be seized.
All things, then, are empty, but even emptiness cannot be seized as a concept: the emptiness of emptiness.
Chih-i founded the T’ien-t’ai school based on an understanding of Nagarjuna’s Two Truths and the Middle Way. Like Nagarjuna, his intention was only to restate what was taught before him, but with an eye toward rephrasing the Dharma with positive language, making it more amenable to his audience, Chinese monks who found the negative Indian dialectic at times difficult.
In developing the Three Truths, Chih-i engaged in his own original thinking, however he was not rejecting, overriding, or replacing Nagarjuna’s Two Truths. He did, obviously, expand the concept. Unfortunately, some schools have asserted a separation of the Three Truths or misunderstood Chih-i’s conclusion, believing he was pointing to a single ultimate dogmatic truth.
To capture Chih-i’s sense of Madhyamaka philosophy, it is important to understand that he viewed all things as being in harmony with each other, and that everything is mutually inclusive of everything else. This reflects not only the general mindset of Chinese Buddhists, influenced by Daoism, but also Chih-i’s profound understanding of pratitya-samutpada or interdependency.
In this way, the ultimate and the relative are different aspects of each other. When the two are seen simultaneously, this is the Middle Way or so-called “Third Truth.” This Chih-i called the “perfect harmony of the Threefold Truth.” There are not three truths, but a single truth understood in a threefold way.
Chih-I then taught that as soon as you say "One Truth", you must next say "No Truth". The idea of three truths in one or One Truth should not become a rationale for seizing onto the ultimate truth as dogma.
There is no One Path or One Way. No “one” view. No One Truth. Two truths are one, three truths are not three, and the one is not one.