Sees nowadays a revival especially in the US.
It is an interpretation of the Torah, the religious mystical system of Judaism, claiming an insight into divine nature. It is a doctrine of esoteric knowledge concerning God, God's creation of the universe and the laws of nature, and the path by which adult religious Jews can learn these secrets.
Kabbalah stresses the reasons and understanding of the commandments and the cause of events described in the Torah. Kabbalah includes the understanding of the spiritual spheres of creation, and the ways by which God administers the existence of the universe.

Jewish mysticism developed with the appearance of the mystical text, the Sefer Yetzirah,. which Jewish sources attribute to Abraham. This book became the object of the systematic study of the elect who were called masters of the Kabbalah. From the 13th century onward Kabbalah branched out into an extensive literature, alongside and often in opposition to the Talmud.

Kabbalah teaches that every Hebrew letter, word, number, and accent of the Hebrew Bible contains a hidden sense; and it teaches the methods of interpretation to get these meanings. Kabbalists traditionally have taught that Kabbalah is the secret part of the law given to Moses on Mt.Sinai. Orthodox Judaism rejects the idea that Kabbalah underwent significant historical development and change.

According to the Hebrew Bible God created not only the world (form), but also the matter (material) out of which it was made. But eminent rabbinic teachers in the Land of Israel held the doctrine of the preexistence of matter. This type of theology, in modern terms, is known as either pantheism or panentheism. Pantheism means God is in everything, panentheism means God created the univers.

Starting from very early times the two attributes of God are justice and mercy, and thus the contrast between justice and mercy became a fundamental doctrine of the Kabbalah.

Other hypostasizations are represented by the ten "agencies" through which God created the world; namely, wisdom, insight, cognition, strength, power, inexorableness, justice, right, love, and mercy. But the most important is "By wisdom God created the heaven and the earth."

The seven preexisting things enumerated in the Torah concern, repentance, paradise and hell, the throne of God, the Heavenly Temple, and the name of the Messiah later more fully developed in the Kabbalah.

The attempts of the mystics to bridge the gulf between God and the world are evident in the doctrine of the preexistence of the soul, and of its close relation to God before it enters the human body a doctrine already taught by the Hellenistic sages

Kabbalah of the Maharal
One of the most important teachers of Kabbalah was Rabbi Judah Loew ben Bezalel (1525-1609) known as the Maharal of Prague. Many of his written works survive and are studied for their deep Kabbalistic insights. During the twentieth century, Rabbi Isaac Hutner (1906-1980) continued to spread the Maharal's teachings indirectly through his own teachings and scholarly publications within the modern yeshiva world.

Kabbalistic understanding of God

Kabbalah teaches that God is neither matter nor spirit. Rather God is the creator of both, but is himself neither. But if God is so different than his creation, how can there be any interaction between the Creator and the created?
This question prompted Kabbalists to envision two aspects of God, (a) God himself, who in the end is unknowable, and (b) the revealed aspect of God who created the universe, preserves the universe, and interacts with mankind. Kabbalists believe that these two aspects are not contradictory but complement one another.
Some Kabbalistic scholars hold that the first aspect of God is all that there really exists; all else is completely nullified to God and therefore an illusion. Depending on how this is explained, such a view can result in panentheism, or pantheism. However, most other Jews who believe in Kabbalah hold that there is an aspect of God that is revealed to the world.
Kabbalists speak of the first aspect of God as "the infinite", "endless", or "that which has no limits". In this view, nothing can be said about this aspect of God. This aspect of God is impersonal.
Kabbalists speak of the second aspect of God as being seen by the universe as ten emanations from God; these emanations are called sefirot. The sefirot mediate the interaction of the ultimate unknowable God with the physical and spiritual world. Some explain the sefirot as stages of the creative process whereby God, from His own infinite being, created the progression of realms which culminated in our finite and physical universe. Others suggest that the sefirot may be thought of as analogous to the fundamental laws of physics. Just as gravity, electro-magnetism, the strong nuclear force, and the weak nuclear force allow for interactions between matter and energy, the ten sefirot allow for interaction between God and the universe.

The Kabbalah's idea of emanations can be compared to the distinction made by fourteenth century Greek Orthodox theologians. They drew a distinction between God's essence and energies, affirming that God was unknowable in His “essence”, but knowable in His “energies”. God's energies are ways in which he can act in the universe, and particularly on people, from the light shining from the face of Moses after Moses descended Mt. Sinai, to the light surrounding Moses, Elijah and Jesus on Mt. Tabor during the transfiguration of Jesus.
God's energies are not separate from God, but were God; however the idea of energies was kept distinct from the idea of the three persons of the Trinity of Christianism

The human soul has three elements
the “animal part” which is linked to instincts and bodily cravings. It enters the physical body at birth and is the source of the physical and psychological nature
the “spirit” which contains the moral virtues and the ability to distinguish between good and evil.
the “higher soul” which separates man from all other lifeforms. It is related to the intellect, and allows man to enjoy and benefit from the afterlife. This part of the soul is provided to all human beings alike at birth and allows to have some awareness of the existence and presence of God.
“Spirit” and “Higher soul” are not “ready” at birth, but can be developed over time;
Their development depends on the actions and beliefs of the individual. They do only fully exist in people awakened spiritually.
Via the “higher soul” one can get an awareness of the divine life force itself. The highest plane of the soul, is that in which one can achieve as full a union with God as is possible.

Dualism
One of the most serious and sustained criticisms of Kabbalah is that it may lead away from monotheism, and instead promote dualism, the belief that there is a supernatural counterpart to God. The dualistic system of good and of evil powers, which goes back to Zoroastrianism, can be traced through Gnosticism; having influenced the cosmology of the ancient Kabbalah before it reached the medieval one.
"The dualistic tendency is, perhaps, most marked in the Kabbalistic treatment of the problem of evil. The profound sense of the reality of evil brought many Kabbalists to posit a realm of the demonic, the Sitra Ahra, a kind of negative mirror image of the "side of holiness" with which it was locked in combat."
However the Zohar indicates that the Sitra Ahra has no power over God, and only exists as a creation of God to give man free choice.

According to Kabbalists, no person can understand the true, unknown nature of God. Rather, there is God that makes Himself known to man, and a hidden one totally removed from man's experience. One can have a reading of this theology as totally monotheistic; however one can also have a reading of this theology as essentially dualistic.

Professor Gershom Scholem writes "It is clear that with this postulate of an impersonal basic reality in God, which becomes a person - or appears as a person - only in the process of Creation and Revelation, Kabbalism abandons the personalistic basis of the Biblical conception of God....It will not surprise us to find that speculation has run the whole gamut - from attempts to re-transform the impersonal En-Sof into the personal God of the Bible to the downright heretical doctrine of a genuine dualism between the hidden Ein Sof and the personal Demiurge of Scripture."

Debate about Kabbalah in Judaism
Despite being criticized by a small number of rabbis, Kabbalah has been a fundamental part of most Jewish theology for many centuries, and is particularly influential in Hasidic and Sephardic thought. Vilna Gaon, the greatest leader of the Mitnagdim former opponents of the Hasidim was also a major Kabbalist and according to Prof Scholem the Kabbalah between 1500 and 1800 was widely considered to be the true Jewish theology. Though many Modern Orthodox Jews do not ascribe to Kabbalah, most other Orthodox Jews still consider it a fundamental part of Jewish thought and belief.

Some rabbis stated that Kabbalah was "worse than Christianity", as it made God into 10, not just into three. The critique, however, is considered untenable. Most followers of Kabbalah never believed this interpretation of Kabbalah. The Christian Trinity concept posits that there are three persons existing within the Godhead, one of whom literally became a human being. In contrast, the mainstream understanding of the Kabbalistic sefirot holds that they have no mind or intelligence; further, they are not addressed in prayer, and they can not become a human being. They are conduits for interaction - not persons or beings.

In the 1960s, Rabbi Saul Lieberman of the Jewish Theological Seminary, is reputed to have introduced a lecture by Scholem on Kabbalah with a statement that Kabbalah itself was "nonsense", but the academic study of Kabbalah was "scholarship". This view became popular among many Jews, who viewed the subject as worthy of study, but who did not accept Kabbalah as teaching literal truths.

In the late 20th and early 21st centuries there has been a revival in interest in Kabbalah in Conservative Judaism. All Conservative Rabbinical seminaries now teach several courses in Kabbalah According to Artson "Ours is an age hungry for meaning, for a sense of belonging, for holiness. In that search, we have returned to the very Kabbalah our predecessors scorned. Kabbalah was the last universal theology adopted by the entire Jewish people, hence faithfulness to our commitment to positive-historical Judaism mandates a reverent receptivity to Kabbalah".

Kabbalah Centre
A recent modern revival has been initiated by the controversial Kabbalah Center founded by Philip Berg in Los Angeles in 1984, and run by him and his sons Yehuda and Michael. With branches worldwide the group has attracted many non-Jews, incl entertainment celebrities like Madonna, Demi Moore, Ashton Kutcher, Mick Jagger and Britney Spears.

Between organized Jewish groups the center is seen almost uniformly as negative, including those that are in favour of broadening the knowledge of Kabbalah. The Centre's teachings are viewed as a mixture of Kabbalistic terminology and various new age teachings, having little to do with authentic Kabbalistic belief.

Kabbalah in non-Jewish society
Kabbalah eventually gained an audience outside of the Jewish community. Nominal-Christian versions of Kabbalah began to develop; by the early 18th century some kabbalah came to be used by some hermetic philosophers, neo-pagans and other new religious groups.

Hermetic Kabbalah
The Western Esoteric or Hermetic Tradition, a precursor to the neo-Pagan and New Age movements, is intertwined with aspects of Kabbalah. Within the Hermetic tradition, much of Kabbalah has been changed from its Jewish roots through syncretism, but core Kabbalistic beliefs are still recognizably present.

Today Kabbalah
Two of the most influential sources spreading Kabbalistic teachings have come from the growth and spread of Hasidic Judaism which can be seen by the growth of the Lubavitch movement, and from the influence of the writings of Rabbi Abraham Isaac Kook (1864-1935) who inspired the followers of Religious Zionism with mystical writings and hopes that interpreted the rise of modern day Zionism as the onset of the atchalta dege'ula - the "beginning of the redemption" of the Jewish people from their exile, in expectation of the arrival of the "final redemption" of the Jewish Messiah. The varied Hasidic works (sifrei chasidus) and Rabbi Kook's voluminous writings drew heavily on the long chain of Kabbalistic thought and methodology.
Gershom Scholem ,a famous scholar and historian of Kabbalah in the twentieth century, echoing many of the arguments of some rabbis, contends that de Leon was the author of the Zohar. The Zohar contains and elaborates upon much of the material found in Sefer Yetzirah and Bahir, and is considered the Kabbalistic work par excellence.