維摩經玄疏 6.58

6.58

Third, clarifying the four gates of the distinctive teaching: if one uses the Madhyamakaśāstra's "also called designation" to discern the four gates, they are the four gates of the distinctive teaching; the four propositions of the Dazhidulun are also acceptable. The intent of these four gates of the distinctive teaching directly comes from the Mahānirvāṇa Sūtra, but is mostly spoken dispersedly. The fourfold-proposition analogy explained with reference to milk is precisely the four gates of the distinctive teaching. If one clarifies that buddha-nature is like milk having the nature of curd, stone having the nature of gold, or the strongman's forehead jewel, that is the gate of existence. If one clarifies that stone has no nature of gold, milk has no nature of curd, and sentient beings and buddha-nature are like empty space, the emptiness of great nirvāṇa, and the emptiness of the city of Kapilavastu, that is the gate of emptiness. The Nirvāṇa [Sūtra] also says: "Regarding buddha-nature being both existent and non-existent: why is it existent? Because all sentient beings possess it. Why is it non-existent? Because it is seen through skillful expedients." And it also compares: "It is like milk both having the nature of curd and not having the nature of curd"—this is the gate of both existence and non-existence. If one clarifies that buddha-nature is precisely the middle way, with the hundred negations both discarded, hence the sūtra compares: "Milk neither has the nature of curd nor lacks the nature of curd"—this is the gate of neither emptiness nor existence. Bodhisattvas of the distinctive teaching distinctively receive the teaching of these four gates, and through it see buddha-nature and abide in great nirvāṇa; therefore the exposition of these four propositions is precisely the four gates of the distinctive teaching. Now I tentatively differentiate the characteristics of the four gates of the distinctive teaching with reference to the text of the Nirvāṇa Sūtra. However, this sūtra text might also be the four gates of the perfect teaching; when we come below to the four gates of the perfect teaching, their similarities and differences will naturally be evaluated.