成唯識論述記 7.395

7.395

述曰：又難外曰：若不許意與五識俱，第六意識取彼五識所緣之境應不明了，彼計五識後方生意識故。今云：緣過去故，如散意識，緣久滅事。此簡宿命智非散意識，緣久滅故彼是明了，為不定過故。此闕有法餘並具足，即八證中第三明了也。

The Commentary states: He also challenges the opponent, saying: If you do not allow the manas to co-arise with the five vijñānas, the sixth mano-vijñāna taking the cognitive object of those five vijñānas would have to be unclear, because you posit that the mano-vijñāna only arises after the five vijñānas. Now [the treatise] says: Because it takes the past as its object, like a distracted mano-vijñāna taking a long-extinguished affair as its object. This excludes the knowledge of past lives (pūrvenivāsānusmṛti-jñāna), which is not a distracted mano-vijñāna; because it takes a long-extinguished [affair] as its object, it is clear—[this exclusion is made] in order to avoid the fault of being inconclusive. This [syllogism] lacks only the subject (dharmin), while the rest [of its components] are complete; this is the third [proof], "clarity," among the eight proofs.