To the Sāmaveda also belongs a very short treatise which was long called the Talavakāra Upanishad, from the school to which it was attached, but later, when it became separated from that school, received the name of Kena, from its initial word. It consists of two distinct parts. The second, composed in prose and much older, describes the relation of the Vedic gods to Brahma, representing them as deriving their power from and entirely dependent on the latter. The first part, which is metrical and belongs to the period of fully developed Vedānta doctrine, distinguishes from the qualified Brahma, which is an object of worship, the unqualified Brahma, which is unknowable:—
To it no eye can penetrate,
Nor speech nor thought can ever reach:
It rests unknown; we cannot see
How any one may teach it us.
The various Upanishads of the Black Yajurveda all bear the stamp of lateness. The Maitrāyaṇa is a prose work of considerable extent, in which occasional stanzas are interspersed. It consists of seven chapters, the seventh and the concluding eight sections of the sixth forming a supplement. The fact that it retains the orthographical and euphonic peculiarities of the Maitrāyaṇa school, gives this Upanishad an archaic appearance. But its many quotations from other Upanishads, the occurrence of several late words, the developed Sānkhya doctrine presupposed by it, distinct references to anti-Vedic heretical schools, all combine to render the late character of this work undoubted. It is, in fact, a summing up of the old Upanishad doctrines with an admixture of ideas derived from the Sānkhya system and from Buddhism. The main body of the treatise expounds the nature of the Ātman, communicated to King Bṛihadratha of the race of Ikshvāku (probably identical with the king of that name mentioned in the Rāmāyaṇa), who declaims at some length on the misery and transitoriness of earthly existence. Though pessimism is not unknown to the old Upanishads, it is much more pronounced here, doubtless in consequence of Sānkhya and Buddhistic influence.
The subject is treated in the form of three questions. The answer to the first, how the Ātman enters the body, is that Prajāpati enters in the form of the five vital airs in order to animate the lifeless bodies created by him. The second question is, How does the supreme soul become the individual soul (bhūtātman)? This is answered rather in accordance with the Sānkhya than the Vedānta doctrine. Overcome by the three qualities of matter (prakṛiti), the Ātman, forgetting its real nature, becomes involved in self-consciousness and transmigration. The third question is, How is deliverance from this state of misery possible? This is answered in conformity with neither Vedānta nor Sānkhya doctrine, but in a reactionary spirit. Only those who observe the old requirements of Brahmanism, the rules of caste and the religious orders (āçramas), are declared capable of attaining salvation by knowledge, penance, and meditation on Brahma. The chief gods, that is to say, the triad of the Brāhmaṇa period, Fire, Wind, Sun, the three abstractions, Time, Breath, Food, and the three popular gods, Brahmā, Rudra (i.e. Çiva), and Vishṇu are explained as manifestations of Brahma.
The remainder of this Upanishad is supplementary, but contains several passages of considerable interest. We have here a cosmogonic myth, like those of the Brāhmaṇas, in which the three qualities of matter, Tamas, Rajas, Sattva, are connected with Rudra, Brahmā, and Vishṇu, and which is in other respects very remarkable as a connecting link between the philosophy of the Rigveda and the later Sānkhya system. The sun is further represented as the external, and prāṇa (breath) as the internal, symbol of the Ātman, their worship being recommended by means of the sacred syllable om, the three “utterances” (vyāhṛitis) bhūr, bhuvaḥ, svar, and the famous Sāvitrī stanza. As a means of attaining Brahma we find a recommendation of Yoga or the ascetic practices leading to a state of mental concentration and bordering on trance. The information we here receive of these practices is still undeveloped compared with the later system. In addition to the three conditions of Brahma, waking, dreaming, and deep sleep, mention is made of a fourth (turīya) and highest stage. The Upanishad concludes with the declaration that the Ātman entered the world of duality because it wished to taste both truth and illusion.
Older than the Maitrāyaṇa, which borrows from them, are two other Upanishads of the Black Yajurveda, the Kāṭhaka and the Çvetāçvatara. The former contains some 120 and the latter some 110 stanzas.
The Kāṭhaka deals with the legend of Nachiketas, which is told in the Kāṭhaka portion of the Taittirīya Brāhmaṇa, and a knowledge of which it presupposes. This is indicated by the fact that it begins with the same words as the Brāhmaṇa story. The treatise appears to have consisted originally of the first only of its two chapters. For the second, with its more developed notions about Yoga and its much more pronounced view as to the unreality of phenomena, looks like a later addition. The first contains an introductory narrative, an account of the Ātman, of its embodiment and final return by means of Yoga. The second chapter, though less well arranged, on the whole corresponds in matter with the first. Its fourth section, while discussing the nature of the Ātman, identifies both soul (purusha) and matter (prakṛiti) with it. The fifth section deals with the manifestation of the Ātman in the world, and especially in man. The way in which it at the same time remains outside them in its full integrity and is not affected by the suffering of living beings, is strikingly illustrated by the analogy of both light and air, which pervade space and yet embrace every object, and of the sun, the eye of the universe, which remains free from the blemishes of all other eyes outside of it. In the last section Yoga is taught to be the means of attaining the highest goal. The gradation of mental faculties here described is of great interest for the history of the Sānkhya and Yoga system. An unconscious contradiction runs through this discussion, inasmuch as though the Ātman is regarded as the all-in-all, a sharp contrast is drawn between soul and matter. It is the contradiction between the later Vedānta and the Sānkhya-Yoga systems of philosophy.