大乘起信論裂網疏 3.120

3.120

The marks of the mind refer precisely to the defiled marks. The essence of the mind refers precisely to the primordial essence that is neither defiled nor pure, on which defilement and purity rely. Defilement also relies on the essence; because it goes against the essence, it is merely termed a mark. Purity also has marks—namely, the greatness of attributes of tathatā; because it accords with the essence, it is directly termed the essence.