大般涅槃經集解 56.18

56.18

案僧亮曰：顯緣因之義，亦能生酪，證無而能生者也。僧宗曰：以求酪之人必取乳故，故知乳是正因也。寶亮曰：縱論以明，理非正答。

Sengliang comments: Revealing the meaning of contributory cause, that it can also produce curd, proving that what is absent can produce. Sengzong comments: Because a person seeking curd must take milk, we know that milk is the direct cause. Baoliang comments: Discussing by concession to clarify it; in principle, this is not the direct answer.