成唯識論述記 9.430

9.430

述曰：體不相違可唯一體，用義分故可說有別，同一種生用分成二，如一識體取境用多故。又何以知者？

The Commentary states: Because their substances do not contradict each other, they can be of a single substance; because their functional senses are distinguished, they can be said to be distinct. They arise from the same seed, yet their functions divide into two, just as the single substance of a consciousness has multiple functions in apprehending objects. Moreover, how is this known?