We have seen that the doctrine of transmigration (gati) through various embodiments, as applicable to all beings, is a fundamental dogma both of Brāhmanism and of Buddhism, though in Buddhism transmigration properly means a mere continuous transformation and reconstruction of the elements (Skandhas) of being ([p. 109]).
The idea is very dimly, if at all, adumbrated in the Mantra portion of the Veda.
It is more clearly traceable in one of the Brāhmaṇas, and distinctly enunciated in the Ćhāndogya Upanishad (V. x. 7) thus:—‘He whose conduct has been good, quickly attains to some good embodiment as a Brāhman, Kshatriya, or Vaiṡya. He whose conduct has been bad, assumes an inferior embodiment, as a dog, a hog, or a Ćaṇḍāla.’ In Manu the theory is fully developed.
Now it is true that in Buddhism this kind of transmigration may be described as a continuous series of incarnations, although genuine Buddhism denies the separate existence of a soul between each incarnation (see [p. 110]).
But the doctrine of repeated incarnations of one individual in six forms of life is quite distinct from the Tibetan Avatāra theory. This theory not only recognizes the separate existence of an immaterial essence or soul, but also teaches that the Head Lāma of certain monasteries is the living, visible embodiment, for the time being, of the continuous descent (avatāra) on earth of a portion of the essence of the canonized Founder of a monastery or of a celestial Bodhi-sattva or Buddha, who will perpetually continue to descend from heaven and re-appear in human forms for the welfare of the world (see [p. 109])[129].
A similar idea, we know, prevails in India, where the doctrine of the descent (avatāra) of portions of the essence of Vishṇu and other gods is common. There is, however, a noteworthy distinction in the Hindū doctrine, because the descents of Vishṇu are not continuous and uninterrupted (see ‘Brāhmanism and Hindūism,’ pp. 47, 107-116); and although every great Hindū teacher is supposed to be the embodiment of a portion of the essence of a deity, each such embodiment is isolated and single.
And here note that one theory is that the continuous descents of Bodhi-sattvas and Buddhas into human forms were effected by means of their third changeable body (Nirmāṇa-kāya, [p. 247]), which belonged to Bodhi-sattvas as well as to Buddhas; or, according to another theory, through rays of light proceeding from the essences of the Bodhi-sattvas, just as the Bodhi-sattvas themselves were held by some to have been generated by rays of light proceeding from the Dhyāni-Buddhas.
Or again, the Dhyāni-Buddhas might incarnate themselves not only intermediately through their Dhyāni-Bodhi-sattvas, but by the transmission of rays of light directly from their own essences into a continuous succession of human beings of pre-eminent sanctity.
Hence it is clear that the Avatāra Lāma is no example of the working of either Hindū metempsychosis or of Buddhist metamorphosis. And indeed, re-birth, through transmigration and transformation, according to the ordinary Hindū and Buddhist theories, is regarded as a kind of natural act, whereas continuous incarnation through the descent of a portion of a celestial essence into human bodies is a supernatural act.
Of course, as we have stated, there were lower and higher Avatāras, corresponding to the difference in rank of Saints and Bodhi-sattvas (see pp. [190], [265]).