("end of the Veda"), a term later interpreted to mean "final goal of the Veda." "Revelation" (çruti) was regarded as including them, while the Sūtras belonged to the sphere of tradition (smṛiti). The subject-matter of all the old Upanishads is essentially the same—the doctrine of the nature of the Ātman or Brahma (the supreme soul). This fundamental theme was expounded in various ways by the different Vedic schools, of which the Upanishads were originally the dogmatic text-books, just as the Brāhmaṇas were their ritual text-books.
The Āraṇyakas and Upanishads represent a phase of language which on the whole closely approaches to classical Sanskrit, the oldest Upanishads occupying a position linguistically midway between the Brāhmaṇas and the Sūtras.
Of the two Brāhmaṇas attached to the Rigveda, the more important is the Aitareya. The extant text consists of forty chapters (adhyāya) divided into eight books called panchikās or "pentads," because containing five chapters each. That its last ten chapters were a later addition appears likely both from internal evidence and from the fact that the closely related Çānkhāyana Brāhmaṇa contains nothing corresponding to their subject-matter, which is dealt with in the Çānkhāyana Sūtra. The last three books would further appear to have been composed at a later date than the first five, since the perfect in the former is used as a narrative tense, while in the latter it still has its original present force, as in the oldest Brāhmaṇas. The essential part of this Brāhmaṇa deals with the soma sacrifice. It treats first (1-16) of the soma rite called Agnishṭoma, which lasts one day, then (17-18) of that called Gavāmayana, which lasts 360 days, and thirdly (19-24) of the Dvādaçāha
