成唯識論述記 4.827

4.827

述曰：第六別有此俱有依，即第七識。何以爾者？自體間斷要託末那方得起故。問：何故不託第八為依？彼不相順，第七有時相順與勢故。問：何不依五識？五識無時此亦有故，不假方生故。

[The Commentary states:] The sixth has a distinct co-existent basis, which is the seventh consciousness. Why is this so? Because its own essence is subject to interruption, and it must rely on the manas in order to be able to arise. Question: Why does it not rely on the eighth as its basis? It is not in alignment with it, whereas the seventh is at times in alignment with it and provides force. Question: Why does it not rely on the five consciousnesses? Because when the five consciousnesses are absent, this [sixth consciousness] still exists, and it does not depend on them to arise.