成唯識論述記 2.515

2.515

述曰：此等比量，義准可知。此三無為體各多者，應是有為，便有品類；此處三品類，非彼品類故；如色等法，非實無為。此即總破三體多訖。

The Commentary states: These inferences can be understood by parity of reasoning. If the substance of each of these three unconditioned phenomena were plural, they would have to be conditioned, and thus would possess distinct classes; because the three classes at this location are not the classes of that location; just like phenomena such as form, they would not be real unconditioned phenomena. This completes the general refutation of the plurality of the three substances.