摩訶止觀 5.122

5.122

佛旨盡淨，不在因、緣、共、離，即世諦是第一義也。又四句俱皆可說，說因亦是，緣亦是，共亦是，離亦是。若為盲人說乳，若貝、若粖、若雪、若鶴，盲聞諸說，即得解乳，即世諦是第一義諦。當知終日說，終日不說；終日不說，終日說。終日雙遮，終日雙照；即破即立，即立即破。經論皆爾。

The Buddha's intent is completely pure, not consisting in cause, condition, combination, or separation; conventional truth itself is the ultimate truth. Furthermore, all four positions can be spoken of: to speak of cause is correct, of condition is correct, of combination is correct, and of separation is correct. As when milk is explained to a blind person as being like a shell, or flour, or snow, or a crane; when the blind person hears these various explanations, he comes to understand milk—conventional truth itself is the ultimate truth. One should know that speaking all day long is not speaking all day long; not speaking all day long is speaking all day long. Negating both all day long is illuminating both all day long; immediate refutation is immediate establishment, and immediate establishment is immediate refutation. Sūtras and treatises are all like this.