大乘起信論裂網疏 3.51

3.51

由第七識恒行不共無明，不如實知真法一故，令諸心王、心所法爾各有能見境相，名為見分，故直名此第七為轉識也。若觀一切境界無是見者，則見無見相，即得入真如門。

Because the constantly active unshared ignorance of the seventh consciousness does not truly know the oneness of the true dharma, it causes all primary minds and mental factors naturally each to possess the ability to see marks of sense-objects, which is named the 'perceiving part'; therefore this seventh is directly named the 'transforming consciousness'. If one contemplates that among all sense-objects there is no such seer, then seeing is without the mark of seeing, and one then attains entry into the aspect of tathatā.