A matter of concern for the Bodhisattva in most of the early Mahāyāna sūtras is that he should not realize the supreme truth (= nirvāna) in the practice of emptiness until he attains Buddhahood. The reason is that a Bodhisattva has to accumulate immeasurable kalpas of merits in order to attain Buddhahood. Realizing the supreme truth ends the circle of existence and thus deprives the Bodhisattva of the chance of attaining Buddhahood. Alongside the development of the Śrāvaka-path into a comprehensive hierarchy with highly advanced theory, the Bodhisattva-path adopted the assertion that the Bodhisattva can attain Buddhahood even after having realized the supreme truth.This contradicts the early statement of not realizing the supreme truth until attaining Buddhahood. In the earlier sūtras “realization of the supreme truth” means “attainment of nirvāna,” but in the later texts, they may not be identified with each other. In some later texts, it is even implied that realization of the supreme truth poses no danger of falling into the Śrāvaka-path as long as the Bodhisattva has loving kindness or is skillful enough not to abide in emptiness. This divergence of opinion about realizing the supreme truth in the Bodhisattvapath is a result of the competition with the Śrāvaka-path. In some cases it reveals a change of the idea of the practice of emptiness. Though with this change the Bodhisattva is still told not to realize nirvāna in order to attain Buddhahood, realization of the supreme truth has become the ideal purpose of the practice of emptiness.
