成唯識論述記 5.741

5.741

述曰：若如所問六皆依意，然唯第六獨依第七不共意根，餘五即無。今依不共以立其名，獨名意識；如五識身亦依於意。依不共根，以得稱故。彼名眼識，不名意識。此亦如是，五義具故。問：如前說依五，八依七，何故第六稱不共依？答：若染淨依及俱有依，七望五、八俱是所依，然近順生不共識者，即唯第六。今言「不共」，意顯近而順生，以六種子必隨七故。餘五等不然，故此得名無相濫失。此為一解。

The Commentary states: If, as questioned, all six rely on the mind, nevertheless only the sixth alone relies on the seventh as its unshared mental faculty, while the other five do not. Now, establishing its name based on the unshared [support], it is uniquely named mental consciousness; just as the five consciousness groups also rely on the mind, yet because they are designated based on unshared faculties, they are called eye-consciousness and so forth, not mental consciousness. This is also like that, because it possesses the five meanings. Question: As stated earlier, the five consciousnesses rely on the fifth, and the eighth relies on the seventh; why is the sixth called relying on an unshared support? Answer: As defiled-purified basis and simultaneous basis, the seventh is a support with respect to both the five and the eighth; however, that which proximately facilitates the arising of the unshared consciousness is exclusively the sixth. Here, 'unshared' indicates proximate and facilitative arising, because the seeds of the sixth must follow the seventh. The remaining five and others are not like this; therefore, this naming has no fault of mutual confusion. This is one explanation.