成唯識論掌中樞要 2.7

2.7

此中三和合皆有生心所功能，說名「變異」。無為無變異，如何有生心所功能？今解：此據有為緣三變異，若無為緣心二變異，無為無變異功能故。又解：依無為有隱、有顯分位變異，不同有為體有變異故。無為有位異故，說名功能，體無功能也。如第七識以第八為根，復為境依，說觸為二和。

Here, when the three come together in harmony, all possess the capacity to generate mental factors, which is called 'alteration'. Since the unconditioned has no alteration, how does it have the capacity to generate mental factors? The present explanation is: this is based on conditioned ālambanas having three alterations; if taking the unconditioned as an ālambana, the mind has two alterations, because the unconditioned lacks the capacity for alteration. Another explanation is: it relies on the unconditioned having positional alteration of being concealed or revealed, unlike the conditioned which has alteration of essence. Because the unconditioned has positional differences, it is described as a capacity, whereas its essence lacks capacity. Just as the seventh consciousness takes the eighth as faculty and again relies on it as object, touch is said to be the coming together of two.