One would think that all Mahāyāna schools would recognize the ability of all people to attain buddhahood since they were based upon the Mahāyāna sūtras wherein the Buddha asserted at the beginning and the end of his teaching that all beings have the buddha-nature and are therefore capable of attaining buddhahood. In fact, the Mahāyāna sūtras did not always guarantee universal buddhahood for all beings. In particular, the arhats and pratyekabuddhas who attained the Hinayāna nirvāṇa were believed to be incapable of taking up the bodhisattva vehicle and attaining buddhahood, particularly since upon passing away they would never again be reborn in the six worlds or anywhere else. This is why Nichiren writes that, “The Hossō and Sanron schools established eight realms, but not ten. Needless to say, they did not know that the ten realms interpenetrate one another.” (Adapted from Murano 2000, p. 14) In other words, because the Dharma Characteristics and Three Treatises schools taught that the arhats and pratyekabuddhas have no realms of their own they simply become extinct upon their deaths and therefore these two schools only acknowledge eight of the ten realms. The Dharma Characteristics school also taught, based upon its own sūtras and commentaries, that people have one of five distinct natures: some people are incorrigible disbelievers (S. icchantika) who are incapable of ever leaving the six lower realms, some are capable of taking up the śrāvaka vehicle, some are capable of taking up the pratyekabuddha vehicle, some are capable taking up the buddha vehicle, and some are able to take up any one of the three vehicles. In this scheme there are some who will never escape saṃsāra and very few who can or will attain buddhahood. Even though these people may have buddha-nature as the true nature of their lives, they do not have the wisdom or virtue to ever realize it.