佛祖統紀 3.22

3.22

此有相生濃淡二義。言相生者。妙玄云。初頓之後。次開於漸。故涅槃云。從佛出十二部經。從十二部經出修多羅。譬從牛出乳從乳出酪云云。次第相生不取濃淡。又云。呼為乳者。意不在淡。以初故本故。言濃淡者。義例云。經中五味。惟喻一代五時濃淡。濃淡雖殊皆從牛出。元草堂云。相生喻教。濃淡喻機。喻教則有次第。從頓開漸。漸入轉深終會於圓。喻機則有優劣。初自聾瘂彈訶淘汰。而卒至得記（文）秖一五味作兩番譬。能譬雖通所譬則局。今論一化次第。唯取相生之義。

This has two senses: mutual production and richness or thinness. Regarding mutual production: the Miaoxuan says, "After the initial sudden, the gradual is next opened. Therefore, the Nirvāṇa [Sūtra] says, 'From the Buddha emerge the twelve divisions of scriptures; from the twelve divisions of scriptures emerge the sūtras,' comparing it to milk coming from cows, curd coming from milk, and so forth. Producing one another in sequence does not take richness or thinness." It also says, "Calling it milk does not aim at thinness; it is because it is the initial and the fundamental." Regarding richness and thinness: the Yili says, "The five flavours in the sutra merely serve as metaphors for the richness and thinness of the five periods across the [Buddha's] lifetime. Although richness and thinness differ, all come from cows." Yuan of Caotang says, "Mutual production is a metaphor for the teachings; richness and thinness is a metaphor for capacities. As a metaphor for the teachings, there is sequence: from the sudden, opening the gradual; entering the gradual and becoming progressively deeper, ultimately converging in the perfect. As a metaphor for capacities, there are superior and inferior: initially deaf and mute, rebuked and sifted out, yet ultimately attaining the prediction [of Buddhahood]." (passage) The single five flavours serve as two sets of metaphors. Although what provides the metaphor is broad, what is illustrated by the metaphor is narrow. Now, in discussing the sequence of the Buddha's entire teaching career, we take solely the sense of mutual production.