 According to traditional Buddhist accounts, by the time the Mahāyāna doctrines arose, roughly in the first century BCE, there were eighteen sub-sects or schools of Sthaviras, the tradition ancestral to the Theravāda (“advocates of the doctrine of the elders”). The number eighteen, though, became conventional in Buddhist historiography for symbolic and mnemonic reasons (Obeyesekere 1991) and, in fact, different Buddhist sources preserve divergent lists of schools which sum up to more than eighteen. The likelihood is that the early formative period of the Buddhist community gave rise to multiple intellectual branches that developed spontaneously due to the geographical extension of the community over the entire Indian subcontinent and subject to the particular problems that confronted each monastic community (saṅgha). Each saṅgha tended to specialize in a specific branch of learning, had its own practical customs and relations with lay circles, and was influenced by the particular territories, economy, and use of language and dialect prevalent in its environment. Indeed, the names of the “eighteen schools” are indicative of their origins in characteristic doctrines, geographical locations, or the legacy of particular founders: for instance, Sarvāstivāda (“advocates of the doctrine that all things exist”), Sautrāntikas (“those who rely on the sūtras”)/Dārṣṭāntikas (“those who employ  examples”),[1]  and Pudgalavāda (“those who affirm the existence of the person”); Haimavatas (“those of the snowy mountains”); or Vātsīputrīyas (“those affiliated with Vātsīputra”) respectively. As noted by Gethin (1998, 52), rather than sects or denominations as in Christianity, “at least some of the schools mentioned by later Buddhist tradition are likely to have been informal schools of thought in the manner of ‘Cartesians,’ ‘British Empiricists,’ or ‘Kantians’ for the history of modern  philosophy.”[2]