成唯識論述記 2.387

2.387

述曰：彼若救言：三世之法是有為故，與生等合；無為體常住，何得有生等？難云：三世之法體有為，即有有為之相合，無為體常住，應有無為之相合。又彼救言：有為有起，可待相合；無為無生，不須相合。難云：無為無起，不須相合；有為體起，何須相合？由如是理徵難不窮，故次論云：彼此異因，不可得故，因者所以。

The Commentary states: If they rescue by saying: 'The phenomena of the three times are conditioned, and therefore combine with birth and the others; the unconditioned substance is permanent, so how could it have birth and the others?' The objection is: If the phenomena of the three times are conditioned in substance and thus combine with the marks of the conditioned, the unconditioned substance is permanent, and thus should combine with the marks of the unconditioned. Again, they rescue by saying: 'The conditioned has an arising, so it can await combination with marks; the unconditioned has no birth, so it does not need to combine.' The objection is: The unconditioned has no arising, so it does not need to combine; the conditioned arises by its own substance, so why does it need to combine? Because through such reasoning the interrogation and objections are endless, the treatise next states: 'Because distinct causes for the two cannot be found.' A cause is a reason.