大般涅槃經義記 4.209

4.209

The above clarified the Three Jewels; next comes the contemplation and examination of the nature of the three vehicles. This text answers the earlier question: "If the three vehicles lack an intrinsic nature, how can they be spoken of?" What was that question? If the three vehicles have no distinct essence or nature, how can the three vehicles be spoken of separately? The Buddha now answers it, clarifying that beings of the three vehicles share the identical buddha-nature and have no other distinct nature. Because they lack a distinct nature, outside of the One Vehicle there are no separate two vehicles. Thus the text below says: "If there were no Buddha in the world, it is not that there would be two vehicles attaining two nirvāṇas; in all the world there is only the One Buddha Vehicle, and therefore there are no two vehicles separately attaining nirvāṇa." Although this passage answers Kāśyapa's earlier question, it concurrently dispels Cunda's doubt regarding impermanence. Because it resolves that doubt, Mañjuśrī raises it again in question.