Then man gains immortality,
Then Brahma is obtained by him (vi. 14).
The story of the temptation of Nachiketas to choose the goods of this world in preference to the highest knowledge is probably the prototype of the legend of the temptation of Buddha by Māra or Death. Both by resisting the temptation obtain enlightenment.
It must not of course be supposed that the Upanishads, either as a whole or individually, offer a complete and consistent conception of the world logically developed. They are rather a mixture of half-poetical, half-philosophical fancies, of dialogues and disputations dealing tentatively with metaphysical questions. Their speculations were only later reduced to a system in the Vedānta philosophy. The earliest of them can hardly be dated later than about 600 B.C., since some important doctrines first met with in them are presupposed by Buddhism. They may be divided chronologically, on internal evidence, into four classes. The oldest group, consisting, in chronological order, of the Bṛihadāraṇyaka, Chhāndogya, Taittirīya, Aitareya, Kaushītaki, is written in prose which still suffers from the awkwardness of the Brāhmaṇa style. A transition is formed by the Kena, which is partly in verse and partly in prose, to a decidedly later class, the Kāṭhaka, Īçā, Çvetāçvatara, Muṇḍaka, Mahānārāyaṇa, which are metrical, and in which the Upanishad doctrine is no longer developing, but has become fixed. These are more attractive from the literary point of view. Even those of the older class acquire a peculiar charm from their liveliness, enthusiasm, and freedom from pedantry, while their language often rises to the level of eloquence. The third class, comprising the Praçna, Maitrāyaṇīya, and Māṇḍūkya, reverts to the use of prose, which is, however, of a much less archaic type than that of the first class, and approaches that of classical Sanskrit writers. The fourth class consists of the later Atharvan Upanishads, some of which are composed in prose, others in verse.
The Aitareya, one of the shortest of the Upanishads (extending to only about four octavo pages), consists of three chapters. The first represents the world as a creation of the Ātman (also called Brahma), and man as its highest manifestation. It is based on the Purusha hymn of the Rigveda, but the primeval man is in the Upanishad described as having been produced by the Ātman from the waters which it created. The Ātman is here said to occupy three abodes in man, the senses, mind, and heart, to which respectively correspond the three conditions of waking, dreaming, and deep sleep. The second chapter treats of the threefold birth of the Ātman. The end of transmigration is salvation, which is represented as an immortal existence in heaven. The last chapter dealing with the nature of the Ātman states that “consciousness (prajnā) is Brahma.”
The Kaushītaki Upanishad is a treatise of considerable length divided into four chapters. The first deals with the two paths traversed by souls after death in connection with transmigration; the second with Prāṇa or life as a symbol of the Ātman. The last two, while discussing the doctrine of Brahma, contain a disquisition about the dependence of the objects of sense on the organs of sense, and of the latter on unconscious life (prāṇa) and conscious life (prajnātmā). Those who aim at redeeming knowledge are therefore admonished not to seek after objects or subjective faculties, but only the subject of cognition and action, which is described with much power as the highest god, and at the same time as the Ātman within us.
The Upanishads of the Sāmaveda start from the sāman or chant, just as those of the Rigveda from the uktha or hymn recited by the Hotṛi priest, in order, by interpreting it allegorically, to arrive at a knowledge of the Ātman or Brahma. The fact that the Upanishads have the same basis, which is, moreover, largely treated in a similar manner, leads to the conclusion that the various Vedic schools found a common body of oral tradition which they shaped into dogmatic texts-books or Upanishads in their own way.
Thus the Chhāndogya, which is equal in importance, and only slightly inferior in extent, to the Bṛihadāraṇyaka, bears clear traces, like the latter, of being made up of collections of floating materials. Each of its eight chapters forms an independent whole, followed by supplementary pieces often but slightly connected with the main subject-matter.
The first two chapters consist of mystical interpretations of the sāman and its chief part, called Udgītha (“loud song”). A supplement to the second chapter treats, among other subjects, of the origin of the syllable om, and of the three stages of religious life, those of the Brahman pupil, the householder, and the ascetic (to which later the religious mendicant was added as a fourth). The third chapter in the main deals with Brahma as the sun of the universe, the natural sun being its manifestation. The infinite Brahma is further described as dwelling, whole and undivided, in the heart of man. The way in which Brahma is to be attained is then described, and the great fundamental dogma of the identity of Brahma with the Ātman (or, as we might say, of God and Soul) is declared. The chapter concludes with a myth which forms a connecting link between the cosmogonic conceptions of the Rigveda and those of the law-book of Manu. The fourth chapter, containing discussions about wind, breath, and other phenomena connected with Brahma, also teaches how the soul makes its way to Brahma after death.
The first half of chapter v. is almost identical with the beginning of chapter vi. of the Bṛihadāraṇyaka. It is chiefly noteworthy for the theory of transmigration which it contains. The second half of the chapter is important as the earliest statement of the doctrine that the manifold world is unreal. The sat by desire produced from itself the three primary elements, heat, water, food (the later number being five—ether, air, fire, water, earth). As individual soul (jīva-ātman) it entered into these, which, by certain partial combinations called “triplication,” became various products (vikāra) or phenomena. But the latter are a mere name. Sat is the only reality, it is the Ātman: “Thou art that.” Chapter vii. enumerates sixteen forms in which Brahma may be adored, rising by gradation from nāman, “name,” to bhūman, “infinity,” which is the all-in-all and the Ātman within us. The first half of the last chapter discusses the Ātman in the heart and the universe, as well as how to attain it. The concluding portion of the chapter distinguishes the false from the true Ātman, illustrated by the three stages in which it appears—in the material body, in dreaming, and in sound sleep. In the latter stage we have the true Ātman, in which the distinction between subject and object has disappeared.