Earlier Buddhist philosophy, associated above all with the Indian thinker Nagarjuna some centuries before Zhiyi, teaches two truths: a conventional truth, the ordinary world of things that can be named, used and spoken of in daily life, and an ultimate truth, the emptiness of any of those named things actually having a fixed, independent nature of their own. Zhiyi's Tiantai school reworked that two part scheme into three. A thing is empty of any nature belonging to it alone, exactly as the earlier teaching already held. It is nonetheless provisionally there, real enough in its own way to be named, used and spoken about meaningfully in the ordinary business of life. And the third, middle truth holds both of the first two truths at once without collapsing either one down into the other, treating emptiness and provisional existence as simultaneously and equally true of the very same thing rather than as two ranked levels where the higher truth simply cancels out or supersedes the lower one. That third, middle truth is precisely what distinguishes the Tiantai formulation from the older two truths scheme it deliberately reworks and builds upon. Zhiyi worked the doctrine out most fully in his commentary on a single verse of Nagarjuna's own writing describing dependent origination, reading that one verse as already containing all three truths at once within itself rather than treating the threefold scheme as a later addition laid on top of Nagarjuna's original teaching.