Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
WE were commanded that, in the sacerdotal blessing, the name of the Lord should be pronounced as it is written in the form of the Tetragrammaton, the shem ha-meforash. It was not known to every one how the name was to be pronounced, what vowels were to be given to each consonant, and whether some of the letters capable of reduplication should receive a dagesh. Wise men successively transmitted the pronunciation of the name: it occurred only once in seven years that the pronunciation was communicated to a distinguished disciple. I must, however, add that the statement, "The wise men communicated the Tetragrammaton to their children and their disciples once in seven years," does not only refer to the pronunciation but also to its meaning, because of which the Tetragrammaton was made a nomen proprium of God, and which includes certain metaphysical principles.
Our Sages knew in addition a name of God which consisted of twelve letters, inferior in sanctity to the Tetragrammaton. I believe that this was not a single noun, but consisted of two or three words, the sum of their letters being twelve, and that these words were used by our Sages as a substitute
for the Tetragrammaton, whenever they met with it in the course or their reading the Scriptures, in the same manner as we at present substitute for it aleph, daleth, etc. [i.e., Adonay, "the Lord"]. There is no doubt that this name also, consisting of twelve letters, was in this sense more distinctive than the name Adonay: it was never withheld from any of the students; whoever wished to learn it, had the opportunity given to him without any reserve: not so the Tetragrammaton: those who knew it did not communicate it except to a son or a disciple, once in seven years, When, however, unprincipled men had become acquainted with that name which consists of twelve letters and in consequence had become corrupt in faith--as is sometimes the case when persons with imperfect knowledge become aware that a thing is not such as they had imagined--the Sages concealed also that name, and only communicated it to the worthiest among the priests, that they should pronounce it when they blessed the people in the Temple; for the Tetragrammaton was then no longer uttered in the sanctuary on account of the corruption of the people. There is a tradition, that with the death of Simeon the just, his brother priests discontinued the pronunciation of the Tetragrammaton in the blessing; they used, instead, this name of twelve letters. It is further stated, that at first the name of twelve letters was communicated to every man; but when the number of impious men increased it was only entrusted to the worthiest among the priests, whose voice, in pronouncing it, was drowned amid the singing of their brother priests. Rabbi Tarphon said, "Once I followed my grandfather to the daïs [where the blessing was pronounced); I inclined my ear to listen to a priest [who pronounced the name], and noticed that his voice was drowned amid the singing of his brother priests."
There was also a name of forty-two letters known among them. Every intelligent person knows that one word of forty-two letters is impossible. But it was a phrase of several words which had together forty-two letters. There is no doubt that the words had such a meaning as to convey a correct notion of the essence of God, in the way we have stated. This phrase of so many letters is called a name because, like other proper nouns, they represent one single object, and several words have been employed in order to explain more clearly the idea which the name represents: for an idea can more easily be comprehended if expressed in many words. Mark this and observe now that the instruction in regard to the names of God extended to the signification of each of those names, and did not confine itself to the pronunciation of the single letters which, in themselves, are destitute of an idea. Shem ha-meforash applied neither to the name of forty-two letters nor to that of twelve, but only to the Tetragrammaton, the proper name of God, as we have explained. Those two names must have included some metaphysical ideas. It can be proved that one of them conveyed profound knowledge, from the following rule laid down by our Sages: "The name of forty-two letters is exceedingly holy; it can only be entrusted to him who is modest, in the midway of life, not easily provoked to anger, temperate, gentle, and who speaks kindly to his fellow men. He who understands it, is cautious with it, and keeps it in purity, is loved above and is liked here below; he is respected by his fellow men; his learning remaineth with him, and he enjoys both this world and the world to come." So far in the Talmud.
[paragraph continues] How grievously has this passage been misunderstood! Many believe that the forty-two letters are merely to be pronounced mechanically; that by knowledge of these, without any further interpretation, they can attain to these exalted ends, although it is stated that he who desires to obtain a knowledge of that name must be trained in the virtues named before, and go through all the great preparations which are mentioned in that passage. On the contrary, it is evident that all this preparation aims at a knowledge of Metaphysics, and includes ideas which constitute the "secrets of the Law," as we have explained (chap. xxxv.). In works on Metaphysics it has been shown that such knowledge, i.e., the perception of the active intellect, can never be forgotten: and this is meant by the phrase "his learning remaineth with him."
When bad and foolish men were reading such passages, they considered them to be a support of their false pretensions and of their assertion that they could, by means of an arbitrary combination of letters, form a shem ("a name") which would act and operate miraculously when written or spoken in a certain particular way. Such fictions, originally invented by foolish men, were in the course of time committed to writing, and came into the hands of good but weak-minded and ignorant persons who were unable to discriminate between truth and falsehood, and made a secret of these shemot (names). When after the death of such persons those writings were discovered among their papers, it was believed that they contained truths; for, "The simple believeth every word" (Prov. xiv. 15).
We have already gone too far away from our interesting subject and recondite inquiry, endeavouring to refute a perverse notion, the absurdity of which every one must perceive who gives a thought to the subject. We have, however, been compelled to mention it, in treating of the divine names, their meanings, and the opinions commonly held concerning them. We shall now return to our theme. Having shown that all names of God, with the exception of the Tetragrammaton (Shem ha-meforash), are appellatives, we must now, in a separate chapter, speak on the phrase Ehyeh asher Ehyeh, (Exod. iii. 14), because it is connected with the difficult subject under discussion, namely, the inadmissibility of divine attributes.