成唯識論述記 2.889

2.889

述曰：第五、重破伏難。初之二句牒彼計非；次三句難，勿善惡業與異熟果為因緣故。汝言諸法各但一種，若異熟果，因但是一種生，善、惡業現行熏果種增時，善、惡業與果應為因緣故。

The Commentary states: Fifth, refuting the implicit defense again. The first two lines repeat their view as incorrect; the next three lines pose a challenge: lest wholesome and unwholesome karma should be cause and condition (hetu-pratyaya) for the vipāka effect. You say each dharma has only a single seed. If a vipāka effect is generated from only one kind of seed as its cause, when actual wholesome or unwholesome karma perfumes and augments that effect's seed, wholesome and unwholesome karma would have to be cause and condition for the effect.