大乘起信論別記 1.40

1.40

Question: Is this nature of innate enlightenment universally the causal nature for both defilement and purity, or is it only the nature of all pure dharmas? If one says it is only the cause of pure dharmas, why does the sūtra say that "the tathāgatagarbha is the cause of both wholesome and unwholesome [dharmas]," and so on at length? If it universally constitutes defilement and purity, why does [the treatise] only speak of being endowed with nature qualities, and not speak of being endowed with defiled afflictions of the nature? Answer: This principle universally serves as the nature for both defilement and purity, and for this reason it only speaks of being endowed with nature qualities. What does this mean? Because the principle is free from a pure nature, it can accord with conditions to produce all defiled dharmas; and because it is free from a defiled nature, it can accord with conditions to produce all pure dharmas. Because it can produce defiled and pure dharmas, it universally serves as the defiled and pure nature; because it is free from defiled and pure natures, it is purely nature qualities. Why is it that being free from defiled and pure natures constitutes all qualities? Because grasping at a defiled or pure nature is entirely conceptual proliferation.