成唯識論述記 3.323

3.323

述曰：此第八識不能具緣十八界故，故有漏位與無漏殊，境有寬狹、勝劣。其六、七識非必有用，即現、比二量是有用心，可應分別。

The Commentary states: Because this eighth consciousness cannot fully cognize the eighteen dhātus, the sāsrava state differs from the anāsrava state, their objects having breadth or narrowness, superiority or inferiority. As for the sixth and seventh consciousnesses, they do not necessarily have functional efficacy; it is the minds of direct perception (pratyakṣa) and inference (anumāna) that have functional efficacy, which should be distinguished.