大乘起信論義記 2.208

2.208

The second, the mark of the perceiver, is the evolving mark. Relying on the preceding karmic mark, it evolves into the perceiver; hence it says “because it is dependent on agitation, there is perceiving.” If one relies on the gate of intrinsic purity, there is no perceiver; hence it says “if unmoved, there is no seeing,” which conversely reveals the meaning that perceiving necessarily relies on agitation. Although such an evolving mark has an apprehending subject, because the object of cognition is subtle, it is not yet distinguishable. As the Mahāyānasaṃgraha says: “The mental consciousness cognizing objects of the three times and objects not of the three times is knowable, whereas the object cognized by this consciousness cannot be known.” Since it says that the object cognized cannot be known, this explains the meaning of the evolving mark of the fundamental consciousness in terms of the apprehending subject.