only wisdom (prajña) can reach nirvana, not samadhi. Bareau notes that this might be the source of the prajñaparamita sutras. Regarding the Ekavyāvahārika branch of the Mahāsāṃghikas, Bareau states that both samsara and nirvana were nominal designations (prajñapti) and devoid of any real substance. According to Nalinaksha Dutt, for the Ekavyāvahārika, all dharmas are conventional and thus unreal (even the absolute was held to be contingent or dependent) while for the Lokottaravada branch, worldly dharmas are unreal but supramundane dharmas like nirvana are real. In Mahayana Buddhism The Mahāyāna (Great Vehicle) tradition, which promotes the bodhisattva path as the highest spiritual ideal over the goal of arhatship, envisions different views of nirvāṇa than the Nikaya Buddhist schools. Mahāyāna Buddhism is a diverse group of various Buddhist traditions and therefore there is no single unified Mahāyāna view on nirvāṇa. However, it is generally believed that remaining in saṃsāra in order to help other beings is a noble goal for a Mahāyānist. According to Paul Williams, there are at least two conflicting models on the bodhisattva's attitude to nirvāṇa. The first model seems to be promoted in the Pañcaviṃśatisāhasrikā Prajñāpāramitā Sūtra and it states that a bodhisattva postpones their nirvāṇa until they have saved numerous sentient beings, then, after reaching Buddhahood, a bodhisattva passes on to cessation just like an arhat (and thus ceases to help others). In this model, their only difference to an arhat is that they have spent aeons helping other beings and have become a Buddha to teach the Dharma. This model seems to have been influential in the early period of Indian Buddhism. Etienne Lamotte, in his analysis of the Mahāprajñāpāramitopadeśa, notes that this text also supports the idea that after entering complete nirvāṇa (parinirvāṇa), a bodhisattva is "able to do nothing more for gods or for men" and therefore he seeks to obtain "wisdom similar to but slightly inferior to that of the Buddhas, which allows him to remain for a long time in saṃsāra in order to dedicate himself to salvific activity by many and varied skillful means." The second model is one which does not teach that one must postpone nirvāṇa. This model eventually developed a comprehensive theory of nirvāṇa taught by the Yogacara school and later Indian Mahāyāna, which states there are at least two kinds of nirvāṇa, the nirvāṇa of an arhat and a superior type of nirvāṇa called apratiṣṭhita (non-abiding). Apratiṣṭhita