大般涅槃經義記 6.12

6.12

問曰：向前內外等中離合為三，今此有為、無為法中何故不然？釋言：准置理亦無傷，但今為明內外二法同是有故，合觀則易，是故第三內外總觀有為、無為。有無位別，合觀則難，故無總矣。

Question: In the preceding treatment of internal, external, and so forth, there was a threefold division of separation and combination; why is this not the case here with conditioned and unconditioned dharmas? Explanation: Analytically establishing it would also not do harm to the principle, but here, in order to clarify that the two dharmas, internal and external, are both existent, combining them in contemplation is easy; therefore the third is the collective contemplation of internal and external. Conditioned and unconditioned differ in status as existence and non-existence, so combining them in contemplation would be difficult; hence there is no collective [contemplation].