According to Jewish faith, G-d is absolutely One. There exists no intrinsic duality or plurality in Him in any form whatsoever.

Kabbalah (Jewish Mysticism) teaches that the beginning of the creative process is the contraction of G-d's infinite light (= the Divine revelation that G-d is all). Then begins a series of steps, the first of which is the projection of a ray of G-d's light (= G-d's revealed Presence) into the apparent vacuum (= apparent state of space "outside" of G-d) which resulted by means of the contraction. Worlds are then created around the ray of light. This is to the cosmos as a soul to the body. For this reason our Sages
say that G-d is to the world as a soul to the body.

After the contraction, G-d appears in many manifestations. These manifestations are relevant only following the initial contraction of G-d's light. From G-d's perspective, the contractions are not to be taken literally.  G-d is, was and always shall be the One and Only. G-d's absolute Oneness is not to be understood in a quantitative sense (not as a "countable one"), He is "One but not in      calculation," He is the absolute One Who creates all "numbers" from one to infinity. The meaning of the contraction is only in relation to our perspective.

After the contraction, when Creation receives its own perspective on reality, G-d may appear to the consciousness of that reality in a dual, triple, quadruple etc. manifestation. A dual manifestation would be two related manifestations, such as the transcendent light of G-d versus the immanent light of G-d. The most essential of G-d's Names, the Tetragrammaton, has four letters.  Each of the four letters is a different manifestation of G-d's presence in reality, His power in Creation and His Providence over Creation. In the same way, G-d sometimes appears as five, six, seven and so forth. Very often we meditate on all the possibilities of appearances from the numbers one to thirteen. There can be even more than these. Each of the twenty-two letters of the Hebrew
alphabet is a manifestation of G-dliness. All of these  possibilities when "traced" back to their ultimate source in G-d's infinite light before contraction "return" to a state of absolute Oneness.

As will be explained, the basic manifestation of three in Judaism is that of G-d, Torah and Israel. There is nothing essentially unique that distinguishes the number three from any other number. As stated above, G-d, the absolute One, can and does appear in any number that He so desires. Each number represents a different secret of reality that He creates (intended, ultimately, to reflect His absolute Oneness).

G-d manifests Himself in different ways. After the initial contraction, if the multi-manifestations of G-dliness remain true and unblemished (by created consciousness, the origin of sin), with no veil separating that manifestation and our consciousness, G-d's unity through His manifestation can be truly appreciated. The state of being after the initial contraction in which quantification in
general does not hinder Divine consciousness, in which reality perceives G-d as the absolute One, is the state of being of the World of Atzilut, "Emanation."

The created consciousness inherent in the three lower worlds of "Creation," "Formation" and "Action" (those worlds whose state of consciousness has fallen from that of Atzilut) does tend to separate, differentiate and divide, and thereby to perceive reality as pluralistic in nature.  This, then, may continue to degenerate into idol worship.

Since the origin of even the lowest of Jewish souls comes from the consciousness of Atzilut, the Jewish soul is able to see through the multi-manifestations of the world around him, and retain perfect faith in G-d's absolute unity (unless he consciously chooses otherwise). The non-Jewish soul may believe, "theoretically," that G-d is One. However, as soon as he pictures G-d as manifest in
reality as he perceives it, G-d appears to him in some form of plurality, the number of which is irrelevant. His mind creates a division in G-d's true unity, a division that tends to degenerate into idol worship, as stated above
.

In the Zohar (the classic text of Kabbalah) and other Jewish sources, we find that there are three (manifestations of G-dliness) which are essentially One: G-d, Israel and the Torah. The Zohar states: "Israel, the Torah and the Holy One Blessed Be He are One." As explained above, before the contraction, from the perspective of G-d (and the origin of the Jewish soul), these three are manifestly revealed as absolutely One.

The Torah is the wisdom and spirit of G-d, of which is said: "He and His wisdom are One." Israel is the son of G-d (the son is the manifest essence of the Father).  Whenever "the son" (of G-d) is referred to in the Bible, that son is "my first born son, Israel." This refers to the entire People of Israel (whose consciousness derives from the spiritual, Divine level of Atzilut, as explained above).

We are further taught in the Zohar that the Torah serves to link the level of the created consciousness of Israel to G-d. The Torah is thus an "intermediate" between the essential "two," the Father and the son (as explained in Kabbalah and Chassidut, the son is born from the "drop" of the wisdom of the Father). Thus, we see that the three "reduce" to two--G-d and Israel. Similarly, the three "expand" to four (in correspondence to the four letters of G-d's essential Name, as mentioned above). Here, the level of Israel divides into the tzadik (the righteous Messianic figure present in every generation) and the Jewish People ("the congregation of Israel") in general. They are referred to, respectively, as the "son" and "daughter" of G-d.

No Jew would ever dream of regarding the People of Israel as an entity unto itself, and praying to it, G-d forbid. Such a thought does not even enter into Jewish consciousness. The same is true with regard to the Torah. The Torah is the holy spirit of G-d. But no Jew would ever dream of relating to the Torah as an independent entity.  The Jewish soul, from Atzilut, never makes the mistake of attaching independent reality to one of G-d's manifestations.

The only One to whom we pray is to G-d Himself. This is one of the thirteen principles of faith as expounded by Maimonides. This is G-d as revealed before the initial contraction. The Jewish consciousness always has the essence of G-d, as revealed before the initial contraction, in the point of faith in his heart.

There is no way (other than conversion to Judaism, when the born-non-Jew is genuinely so aroused) that the consciousness of a non-Jew can reach the level of pre-contraction. The consciousness of the non-Jew derives from one of the three lower worlds of Beriah ("Creation"), Yetzirah ("Formation"), Asiyah ("Action"), which perceive plurality as plurality. From this perspective, the "Father," "son," and "spirit" appear as three separate entities. The claim, from the perspective of non-Jewish consciousness, that they are essentially one is immaterial. The non-Jewish consciousness is unable to truly unify the three and to understand that their essence is one. They perceive each of the three as possessing such a strong "personality" of its own that it can exist independently. This is idolatry.

The non-Jewish attempt to parody this ultimate secret of three which is One totally destroys the authenticity of the paradox of the concept. When the consciousness is not one of Atzilut, the "son" becomes distinct from the Father and the "holy spirit" also becomes distinct as a personality and the non-Jewish soul falls into idolatry. This is forbidden for the non-Jew as well as for the Jew. The prohibition against idolatry is the most important of the Seven Noahide Commandments.

It is written (Proverbs 8:22-31): "G-d possessed me at the beginning of His way...When He prepared the heavens, I was there...When He marked out the foundations of the earth...Then I was beside Him...and my delight (was) with the sons of men."

The Torah is the subject (the "speaker") in these verses. As explained above, when relating to the manifestation of any number of entities following the initial contraction of G-d's infinite light, we must bear in mind that prior to the contraction those manifestations are absolutely one. The paradox of the Torah, after the contraction, saying "I was beside G-d" or "I was the tool of G-d in Creation" remains. The ultimate, absolute root of the souls of Israel, the son of G-d, also exists before the initial contraction, absolutely one with G-d. This paradox is one that a consciousness not from Atzilut cannot appreciate.

We shall now study a verse from Isaiah that is often misinterpreted in order to create a misrepresentation with regard to G-d's absolute Unity. When the text is studied with its traditional translation to Aramaic, Targum Yonatan, and the traditional commentaries of Rashi, Ibn Ezra, and Radak, its true meaning is clear.

In Isaiah (48:12-16) we read:

(12) Listen to Me, O Jacob, and Israel whom I have called.

I am He, I am the First, I am also the Last.

(13) My hand has also laid the foundation of the earth, and My right hand has spanned the heavens.
When I call them, they stand up together.

(14) All of you: assemble yourselves and hear, which among them has declared these things?
He whom the L-rd loves, he will do His pleasure on Babylon, and his arm shall be on the Kasdim.

(15) I, even I, have spoken; indeed, I have called him. I have brought him, and he shall succeed in his way.

(16) Come near to Me, hear this: I have not spoken in secret from the beginning.
From the time that it was, there have I been.  And now the L-rd G-d and His spirit have sent me.

The above verses in Isaiah form an integral portion in the text. In the Masoretic Bible text, they appear as a separate unit (parashah).

Unlike its false interpretation, there is no appearance here of three divine entities. Let us begin to analyze these verses.

First we must note that the grammatical division of almost every verse in the Bible is into two distinct sentences. This phenomenon is marked by the strongest cantillation note, the etnachta.

The second sentence of the last verse reads, "And now the L-rd G-d has sent me and His spirit." The Targum and Rashi explain that this final sentence is a change of subject. Up until this point, the last word of the previous sentence reads, "There am I." This concludes the words of G-d which make up the entire portion until this point. The final sentence presents the words of the prophet.
Obviously the prophet is not identified as G-d. Like every Jewish soul, he is a son of G-d. This is the most basic  difference between Judaism and any other misconception of religion.

This sentence literally reads "And now, the L-rd G-d has sent me, and His spirit." The Radak explains that the prophet sometimes hears a direct voice spoken by G-d, and sometimes he may experience the vision of an angel sent to speak with him. According to this, "His spirit" means the angel sent to speak with him. The meaning of the verse is thus: "G-d has sent me, together with the angel who I saw in my prophecy, who was sent by G-d, to speak with me and to send me."

Another reading of the word "His spirit" is "the spirit within me." The prophet relates that he became inspired. This is the explanation of Rav Sa'adiah Gaon. The vav in the word v'rucho ("and His spirit") translates as "with His spirit." The meaning of the verse according to this reading is: "G-d has aroused His spirit within me, and with the power of that spirit has sent me to prophesize to the people. It is obvious that there are not three different divinities, G-d forbid, expressing themselves in these        verses.

In the first verse of this portion, the word "I," (ani) is repeated three times. "I am He, I am the first and I am even the last." The fact that this word is repeated three times means, "I am one and the same." Verse 15 begins with the word "I" repeated twice. Certainly if we meditate upon this in depth, "I, I" means two complementary manifestations of the same "I," as if the same person were speaking from two vantage points. If the first verse reads "I am He, I am the first and I am the last," it means that "I appear as the first, and I appear as the last, and I am He." There is no way, with simple common sense, to misunderstand this.

According to Jewish mysticism, there are a number of beautiful and significant secrets in this passage from Isaiah.

First of all, as we know, the number seven is most significant in the Torah. The numerical value of the very word for "I" (ani) in reductive gematria is 7 (alef = 1, nun = 5, yud = 1; 1 plus 5 plus 1 = 7.)

The word "I" is repeated seven times in the entire portion.  It appears three times in the first verse, once in the second verse, not at all in the third verse, twice at the beginning of the fourth verse, and once as the conclusion of the first sentence of the fifth verse, "There am I." In Kabbalah, the word "there" is always a symbol of malchut, kingdom, which is the seventh, final level of the seven attributes of the heart. The seventh level is explicitly "There am I." The verse then turns to the words of the prophet speaking. From this we can understand that G-d has seven manifestations, or "I"'s, and not only three.

Secondly, the Hebrew word for "eye" is ayin. In Hebrew, the letter ayin always alludes to the letter alef enclothed within it (both due to the phonetic similarity of the two letters as well as their numerical ratio of 1:70). The internal essence of the eye is ayin (with the letter alef replacing the letter ayin), the Divine "nothingness," which is a permutation of the word ani, "I." Just as in English the words "I" and "eye" sound the same, in Hebrew there is a very close relation between the words ani, "I," and ayin "eye." In the Bible we find that G-d has seven eyes (Zachariah 4:10). This is obviously not meant to be taken literally, but clearly conveys a secret. In His Providence, G-d overlooks and judges creation from seven perspectives (corresponding to the seven attributes of the heart). Just as G-d possesses seven "eyes," so does He reveal Himself in this portion with seven "I"s. In   meditation upon this portion in Isaiah, we become much more involved with the secret of the number seven than with the number three.

Secondly, the Hebrew word for "eye" is ayin. In Hebrew, the letter ayin always alludes to the letter alef enclothed within it (both due to the phonetic similarity of the two letters as well as their numerical ratio of 1:70). The internal essence of the eye is ayin (with the letter alef replacing the  letter ayin), the Divine "nothingness," which is a permutation of the word ani, "I." Just as in English the words "I" and "eye" sound the same, in Hebrew there is a very close relation between the words ani, "I," and ayin
"eye." In the Bible we find that G-d has seven eyes (Zachariah 4:10). This is obviously not meant to be taken literally, but clearly conveys a secret. In His Providence, G-d overlooks and judges creation from seven perspectives (corresponding to the seven attributes of the heart). Just as G-d possesses seven "eyes," so does He reveal Himself in this portion with seven "I"s. In mediation upon this portion in Isaiah, we become much more involved with the secret of the number seven than with the number three.

Finally, in the first verse, "I" appears as the sixth, eighth and eleventh word from the beginning. In the second verse it appears as the ninth word. In the fourth verse it appears as the first and second words. In the final verse it appears as the twelfth word. If we add all these positional numbers together, we arrive at 25 (52) in the first verse, and 24 (one less than 25) in the remaining verses. (25 is also the value of the word ani in positional numbering:  Alef, the first letter is one, nun, the fourteenth letter, is 14, and yud, the tenth letter, is ten; together, they equal 25.) When 24 is added to 25 we find that the sum of all the seven positional appearances of the word "I" equals 49, which is 72. This emphasizes the secret of the number 7. In the words of our Sages, "All the sevens are dear."

If we count the positional values from the end of each verse, they add up to 39. This is 3 times 13. 49 is 7 times 7.  The two numbers, 7 and 13 generally appear as a pair in the Torah. 3 times 13 equals the value of Havayah echad, "G-d is One." Havayah (26) is two times echad (13). The word echad means "one." The very value of G-d's essential Name, Havayah, which is 26, is 2 times "one."  Intrinsic to G-d's Name are two complementary manifestations of Oneness. Havayah echad, "G-d is One," equals three times "one" (echad). We thus observe that the value of three ones, echad, echad, echad, is the exact value of the positional numbers of the seven different ani's in the portion.

Another very significant phenomenon about the portion is that in the entire portion of 5 verses there are exactly 64 words. 64 = 82. In this entire portion, G-d's Name Havayah is explicitly stated three times. The pronoun "I" (G-d) is stated 7 times. If we remove the three times that G-d's Name appears, 61 words remain. The number 61 is the full numerical value of the word ani, "I." Thus the entire portion hints at the phrase, Ani Havayah, "I am G-d."

The first appearance of G-d's Name in these verses is the seventh word from the end of the verse. The other two appearances of G-d's Name are the third and fourth words, respectively, from the end of the verse. Three and four also equal seven. Here seven is again hinted to twice in the positional values of G-d's Name.

All these secrets blend together. In our consciousness, where the Torah has thousands of words and signs, each of them is a manifestation of G-dliness and Unity. It all blends into a perfection of G-d is One.