Pitṛputra-samāgama Sūtra Commentary (151)

What is Nirvana?

The path to nirvana should be understood as follows. The fundamental basis upon which nirvana initially relies is the One True Dharma Realm, the dharma of ālaya-vijñāna. Without ālaya-vijñāna, there would be no possibility of discussing the four kinds of nirvana. It is only by relying on the ālaya-vijñāna Tathāgatagarbha Dharma Realm that all dharmas are understood to be empty, quiescent, and without characteristics; hence, there is nothing to seek. These principles pervade the bounds of space; in whichever world throughout the expanse of space, this is the same truth: all dharmas are empty. This principle applies universally to all boundaries of space; it is always thus.

Nirvana is divided into four kinds: Nirvana with Remainder, Nirvana without Remainder, Nirvana of the Intrinsically Pure Mind, and Non-abiding Nirvana. The nirvana of the Small Vehicle (Hinayana) seeks to extinguish all dharmas. Nirvana is a provisional designation, referring to the attainment of a state of non-arising and non-ceasing. It is merely a state or property, not a truly existent dharma.

The truly existent dharma is Tathāgatagarbha. Upon the substance of Tathāgatagarbha manifests a property of non-arising and non-ceasing, an immutable property—this is nirvana. When an Arhat enters Nirvana without Remainder, there is no Arhat; only his Tathāgatagarbha mind remains, abiding in a state of non-arising and non-ceasing. That is called nirvana; therefore, nirvana is also a provisional designation. Only the Mind of True Suchness, the Tathāgatagarbha mind, is real. It is the true dharma, the real dharma; all else is provisional dharmas.

The Buddha also stated this in the Mahāparinirvāṇa Sūtra: just as Suchness (Tathatā) is also a property or state, Suchness is the real and thusness property manifested by ālaya-vijñāna Tathāgatagarbha; it is a noun. True Reality (Dharma-dhātu) is the truly existent aspect of Tathāgatagarbha. Upon this truly existent aspect manifests a real nature and an immutable thusness property—this is Suchness. Therefore, it is said that nirvana proceeds together with emptiness; when emptiness is fully realized, one enters Nirvana without Remainder. This emptiness means abiding in the realm and state of the non-arising and non-ceasing Tathāgatagarbha; this is called nirvana.