The Vedas are called shruti — heard, not composed — and were transmitted orally with astonishing fidelity for a millennium before writing, using recitation patterns that scramble word order deliberately so errors cannot survive. The four collections are ritual manuals; the Upanishads at their end are something else entirely, turning from sacrifice to the question of what the self is, and it is the Upanishads that most Hindu philosophy actually builds on. Almost no Hindu reads the Vedas; nearly every Hindu tradition claims their authority.