compilation. The ordinary historical relation of Brāhmaṇā and Sūtra is here reversed, the second book of the Gopatha Brāhmaṇa being based on the Vaitāna Sūtra, which stands to it practically in the relation of a Saṃhitā. About two-thirds of its matter have already been shown to be taken from older texts. The Aitareya and Kaushītaki Brāhmaṇas have been chiefly exploited, and to a less extent the Maitrāyaṇī and Taittirīya Saṃhitās. A few passages are derived from the Çatapatha, and even the Panchaviṃça Brāhmaṇa.
Though the Upanishads generally form a part of the Brāhmaṇas, being a continuation of their speculative side (jñāna-kāṇḍa), they really represent a new religion, which is in virtual opposition to the ritual or practical side (karma-kāṇḍa). Their aim is no longer the obtainment of earthly happiness and afterwards bliss in the abode of Yama by sacrificing correctly to the gods, but release from mundane existence by the absorption of the individual soul in the world-soul through correct knowledge. Here, therefore, the sacrificial ceremonial has become useless and speculative knowledge all-important.
The essential theme of the Upanishads is the nature of the world-soul. Their conception of it represents the final stage in the development from the world-man, Purusha, of the Rigveda to the world-soul, Ātman; from the personal creator, Prajāpati, to the impersonal source of all being, Brahma. Ātman in the Rigveda means no more than "breath"; wind, for instance, being spoken of as the ātman of Varuṇa. In the Brāhmaṇas it came to mean "soul" or "self." In one of their speculations the prāṇas or "vital airs," which are supposed to be based on the ātman, are identified with the gods, and so an ātman comes to be attributed to the universe.