The four Hebrew letters , sometimes known as the Tetragrammaton, are the heart and soul of the Hebrew Bible. The pronunciation of this word has been a closely held secret. In Hebrew, the four letters, like the English YHWH, are all consonants. The ancient Hebrews did not have symbols for the vowels. When the vowels were added later, the vowels for another word were substituted so as not to give away the secret of the true pronunciation, which Jews regard as expressing not merely the name but the essence of God imbued with mystical if not magical power.

The Tetragrammaton is generally rendered in English as Yahweh, pronounced "yaway." This produces a full cycle of phase shift, the complete spectrum of vowel sounds. At certain points in this spectrum which are normally glided over too quickly to notice, a voice quite distinct from that of the cantor emerges: a clear, bell-like ringing, which ascends and descends in arpeggios as the spectrum from long E to O is pronounced.

This is not just one amongst the many names for God in the Old Testament. Scholars identify the oldest parts of the OT, the "Yahwistic" tradition, by the use of the Tetragrammaton. One does not have to look far to find it: wherever the Christian Old Testament uses "LORD" in all capital letters, it stands for the Tetragrammaton. Most tellingly, Exodus 3:15 uses the Tetragrammaton when God says to Moses, "This is my name for all time, and thus I am to be invoked for all generations to come."

The Judaic Taboo

Why, then, does the priestly caste prefer that the common people (at least) not invoke Yahweh? If it is due to reverence for the divine epithet then why is YHWH singled out for suppression, rather than Elohim or El Shaddai? Because Yahweh is the particular name by which God instructed Israel to inoke Him? Revering God by violating God's explicit instructions makes no sense at all. Reverence for the holy Name not only has no solid scriptural support, it is flatly contradicted by the frequent repetition of the Tetragrammaton throughout Psalms: are we to believe David was being irreverant? Not only does the choral form of the Psalms indicate that it was intended to be sung, there are specific directions to the choirmaster in the text!

My own anwer this question has evolved from my own experience with the name.  I no longer believe that the taboo on pronouncing the Holy Name originated as a priestly power play.  My sense is that a true experience of oneness with God means escaping from the dualism that is the essence of consciousness.  This is a radical kind of ecstasy, quite literally stepping outside of one's self. 

The challenge is to construct a personal myth which bridges this hiatus in consciousness: to return changed, yet not too changed.  Gershom Scholem's book, Shabbatai Zvi: the mystical messiah, is a fascinating lesson in one who became so changed that he left his community and perhaps himself behind.  It is understandable that Judaism, as the community thus betrayed, has publicly turned away from Kabbalah, the practice of Zvi and other remarkable men such as the Ba'al Shem Tov, "Master of the Holy Name".

The late Hasidic teacher Dovid Din put it this way:  "The difference between Judaeo-Christian mysticism and Hindu mysticism is that the Hindu seeks to free himself from his identity, to lose himself  in Oneness.  We on the other hand believe that as man is created in the image of the creator, we should not lightly cast aside our individuality.  Our goal is to make the journey to oneness, and to return."