大般涅槃經義記 8.267

8.267

自下第五師子以其緣正二因證性本有，如來對破。師子先問「眾生有性如乳中酪」，自立有義。「若乳無酪云何佛說有二因」等，破無成有。「虛空無性故無緣因」，舉無顯有。佛破有三：一就喻破有、二就法破有、第三雙就法喻破有。初中三番：第一如來對問正破。「若使乳中定有酪者，何須緣因」，待緣方有明知本無。

From here below is the fifth part, where Siṃhanāda uses the two causes—the conditioning cause and the direct cause—to prove that the nature is fundamentally present, and the Tathāgata refutes this in response. First, Siṃhanāda asks, "Sentient beings possess the nature just as milk contains curds," asserting on his own part the meaning of presence. "If milk lacks curds, why did the Buddha speak of having two causes?" and so forth refutes non-existence to establish existence. "Empty space lacks a nature and therefore lacks a conditioning cause" adduces non-existence to reveal existence. The Buddha's refutation has three parts: first, refuting existence with respect to the analogy; second, refuting existence with respect to the doctrine; third, refuting existence with respect to both the doctrine and the analogy together. Within the first part, there are three rounds. In the first round, the Tathāgata directly refutes [him] in response to the question: "If milk definitely had curds within it, why would it require conditioning causes?" Depending on conditions before it exists clearly shows it is fundamentally absent.