At the time when another class of writings (the Puranas) were added to the inspired code of Hinduism, for a similar reason Om is their introductory word.
That the mysterious power which, as the foregoing quotation from the law-book of Manu shows, was attributed to this word must have been the subject of early speculation, is obvious enough. A reason assigned for it is given by Manu himself. "Brahma," he says, "extracted from the three Vedas the letter a, the letter u, and the letter m (which combined result in Om), together with the (mysterious) words Bhuh (earth), Bhuva (sky), and Swah (heaven);" and in another verse: "These three great immutable words, preceded by the syllable Om, and (the sacred Rig Veda verse called) Gayatri, consisting of three lines, must be considered as the mouth (or entrance) of Brahman (the Veda)," or, as the commentators observe, the means of attaining final emancipation; and "The syllable Om is the supreme Brahman. (Three) regulated breathings, accompanied with the mental recitation of Om, the three mysterious words Bhuh, Bhuvah, Swah and the Gayatri, are the highest devotion."
"All rites ordained in the Veda, such as burnt and other sacrifices, pass away, but the syllable Om must be considered as imperishable; for it is (a symbol of) Brahman (the supreme spirit) himself, the Lord of Creation." In these speculations Manu bears out, and is borne out by, several Upanishads. In the Katha-Upanishad for instance, Yama, the god of death, in replying to a question of Nachiketas, says: "The word which all the Vedas record, which all the modes of penance proclaim, desirous of which religious students perform their duties, this word I will briefly tell thee—it is Om. This syllable means the (inferior) Brahman and the supreme (Brahman). Whoever knows this syllable obtains whatever he wishes." And in the Pras'na-Upanishad the saint Pippalada says to Satyakama: "The supreme and the inferior Brahman are both the word Om; hence the wise follow by this support the one or the other of the two. If he meditates upon its one letter (a) only, he is quickly born on the earth; is carried by the verses of the Rig Veda to the world of man; and, if he is devoted there to austerity, the duties of a religious student and faith, he enjoys greatness. But if he meditates in his mind on its two letters (a and u), he is elevated by the verses of the Yajur Veda to the intermediate region; comes to the world of the moon and, having enjoyed there power, returns again (to the world of man). If, however, he meditates on the supreme spirit by means of its three letters (a, u, and m) he is produced in light in the sun; as the snake is liberated from its skin, so is he liberated from sin." According to the Mandukya-Upanishad the nature of the soul is summarized in the three letters a, u, and m in their isolated and combined form—a being Vaiswanara, or that form of Brahman which represents the soul in its waking condition; a, Taijasa, or that form of Brahman which represents it in its dreaming state; and m, Piajna, or that form of Brahman which represents it in its state of profound sleep (or that state in which it is temporarily united with the supreme spirit); while a, u, m combined (i.e., Om), represent the fourth or highest condition of Brahman, "which is unaccountable, in which all manifestations have ceased, which is blissful and without duality. Om therefore, is soul, and by this soul, he who knows it, enters into (the supreme) soul." Passages like these may be considered as the key to the more enigmatic expressions used; for instance, by the author of the Yoga philosophy where, in three short sentences, he says his (the supreme lord's) name is Pranava (i.e., Om); its muttering (should be made) and reflection on its signification; thence comes the knowledge of the transcendental spirit and the absence of the obstacles (such as sickness, languor, doubt, &c., which obstruct the mind of an ascetic). But they indicate, at the same time, the further course which superstition took in enlarging upon the mysticism of the doctrine of the Upanishads. For, as soon as every letter of which the word Om consists was fancied to embody a separate idea, it is intelligible that other sectarian explanations were grafted on them to serve special purposes. Thus, while Sankara, the great theologian and commentator on the Upanishads, is still contented with an etymological punning by means of which he transforms a into an abbreviation of apti (pervading), since speech is pervaded by Vaiswanara; u into an abbreviation of utkartha (superiority), since Taijasa is superior to Vaiswanara; and m into an abbreviation of miti (destruction), Vaiswanara and Taijasa, at the destruction and regeneration of the world, being, as it were, absorbed into Prajna—the Puranas make of a, a name of Vishnu; of u, a name of his consort "Sri;" and of m, a designation of their joint worshipper; or they see in a, u, m, the Triad—Brahm, Vishnu, and Siva; the first being represented by a, the second by u, and the third by m—each sect, of course, identifying the combination of these letters, or Om with their supreme deity. Thus, also, in the Bhagavadgita, which is devoted to the worship of Vishnu in his incarnation as Krishna, though it is essentially a poem of philosophical tendencies based on the doctrine of the Yoga, Krishna in one passage says of himself that he is Om; while in another passage he qualifies the latter as the supreme spirit. A common designation of the word Om—for instance, in the last-named passages of the Bhagavadgita is the word Pranava, which comes from a so-called radical nu, "praise," with the prefix pra amongst other meanings implying emphasis, and, therefore, literally means "eulogium, emphatic praise." Although Om, in its original sense as a word of solemn or emphatic assent, is, properly speaking, restricted to the Vedic literature, it deserves notice that it is now-a-days often used by the natives of India in the sense of "yes," without, of course, any allusion to the mystic properties which are ascribed to it in the religious works. Monier Williams gives the following account of the mystic syllable Om: "When by means of repeating the syllable Om, which originally seems to have meant 'that' or 'yes,' they had arrived at a certain degree of mental tranquillity, the question arose what was meant by this Om, and to this various answers were given according as the mind was to be led up to higher and higher objects. Thus, in one passage, we are told at first that Om is the beginning of the Veda, or as we have to deal with an Upanishad of the Shama Veda, the beginning of the Shama Veda; so that he who meditates on Om may be supposed to be meditating on the whole of the Shama Veda.
"Om is the essence of the Shama Veda which, being almost entirely taken from the Rig Veda, may itself be called the essence of the Rig Veda. The Rig Veda stands for all speech, the Shama Veda for all breath or life; so that Om may be conceived again as the symbol of all speech and all life. Om thus becomes the name not only of all our mental and physical powers, but is especially that of the living principle of the pran or spirit. This is explained by the parable in the second chapter, while in the third chapter that spirit within us is identified with the spirit in the sun.
"He, therefore, who meditates on Om, meditates on the spirit in man as identical with the spirit in Nature or in the sun, and thus the lesson that is meant to be taught in the beginning of the Khandogya Upanishad is really this that none of the Vedas, with their sacrifices and ceremonies, could ever secure the salvation of the worshipers. That is, the sacred works performed, according to the rules of the Vedas, are of no avail in the end, but meditation on Om, or that knowledge of what is meant by Om, alone can procure true salvation or true immortality.
"Thus the pupil is led on step by step to what is the highest object of the Upanishads—namely, the recognition of the self in man as identical of the highest soul.
"The lessons which are to lead up to that highest conception of the universe, both subjective and objective, are, no doubt, mixed up with much that is superstitious and absurd. Still the main object is never lost sight of. Thus, when we come to the eighth chapter, the discussion, though it begins with Om ends with the question of the origin of the world, and the final answer—namely, that Om means Akasa, ether, and that ether is the origin of all things."
Dr. Lake considers electricity as the akas, or the fifth element of the
Hindus.
I shall now give my own opinion on the mystic syllable Om.
Breath consists of an inspiration termed puraka, an interval termed kumbhaka, and an expiration called rechaka. When the respiration is carried on by the right nostril, it is called the pingala; when it is carried on by the two nostrils, it is named the susumna; and when it is carried on by the left nostril, it is called ida.