十不二門指要鈔 2.54

2.54

二、法性下，明染淨用者，體既全轉、用亦敵翻，法性既作無明，全起無明之用，用既縛著名之為染；無明若為法性，全起法性之用，用既自在名之為淨。

Second, from "Dharma-nature..." down, clarifying the function of defilement and purity: since the substance is completely turned, the function is also symmetrically overturned. Since Dharma-nature acts as ignorance, it gives rise entirely to the function of ignorance; since the function is bound by attachment, it is called defilement. If ignorance acts as Dharma-nature, it gives rise entirely to the function of Dharma-nature; since the function is unhindered, it is called purity.