成唯識論述記 4.130

4.130

述曰：《莊嚴論》言同行者，同一時行也。設許前難佛滅後方造大乘，何故與汝小乘之教一時俱行？量云：諸大乘經，佛滅即行；許明無我理契經攝故；如《增一》等。然成佛說諸大乘經真是佛說；許佛滅後本來俱行故；如《增一》等。又小乘經，應非佛說；與大乘經本俱行故；如汝許大乘經。雖違大乘自宗，以許彼經是佛語故，然義逼應爾，為相違過，何故大乘獨非佛語，而小乘教是佛語耶？彼許大乘一時俱有，不須成立佛滅即行。問：若是佛語，何故聲聞等不信樂？不聞說耶？彼無廣解。

The Commentary states: What the Mahāyānasūtrālaṃkāra calls "circulating together" means circulating at the same time. Even granted the previous objection that the Mahāyāna was fabricated only after the Buddha's parinirvāṇa, why did it circulate concurrently at the same time as your Hīnayāna teaching? The syllogism runs: Thesis: All Mahāyāna sūtras circulated immediately upon the Buddha's parinirvāṇa; Reason: Because they are accepted as subsumed under the sūtras that reveal the principle of selflessness; Example: Like the Ekottarikāgama and so forth. Then, establishing that they are the Buddha's speech: Thesis: All Mahāyāna sūtras are truly the Buddha's speech; Reason: Because they are accepted as having circulated concurrently from the origin after the Buddha's parinirvāṇa; Example: Like the Ekottarikāgama and so forth. Furthermore: The Hīnayāna sūtras ought not to be the Buddha's speech; because they have circulated concurrently from the origin with the Mahāyāna sūtras; like the Mahāyāna sūtras accepted by you. Although this contradicts the Mahāyāna's own tenets, since we accept those sūtras to be the Buddha's word, yet pressed by reason it should be so, producing the fallacy of contradictory [consequence]: Why alone would the Mahāyāna not be the Buddha's word, while the Hīnayāna teaching is the Buddha's word? Since the opponent accepts that the Mahāyāna existed concurrently at the same time, there is no need to establish that it circulated immediately upon the Buddha's parinirvāṇa. Question: If it was the Buddha's speech, why did the śrāvakas and others not believe and take delight in it, nor hear it spoken? [Answer:] They lacked vast understanding.