大乘起信論義記 2.180

2.180

問：所現似法，豈不由彼執實有耶？答：雖由執實，然似恒非實，如影由質，影恒非質。鏡中現影，不現於質，不現質故，故云空鏡；能現影故，是因熏也。

Question: Do the resembling phenomena that are manifested not arise due to that clinging to real existence? Answer: Although they arise due to clinging to the real, the resembling is perpetually not real, just as a shadow arises due to a physical form, yet the shadow is perpetually not the physical form. In a mirror, shadows appear, but the physical form does not appear. Because it does not manifest the physical form, it is called the 'empty mirror'; because it can manifest shadows, it is the 'perfuming as cause.'