The following is condensed from Colin Low’s excellent explanation in the Quabbalah FAQ:
“Many people who study Kabbalah are not Jewish. This has been happening for 500 years or so. It is difficult to know what to call this variant of Kabbalah. "Non-Jewish" is inaccurate, as I have personally known several Jews who opted for Hermetic Kabbalah in preference to the traditional variety! At one time it was called "Christian" Kabbalah, but this is also very misleading.
The origin of this variant can be placed in Renaissance Italy in the last decade of the 15th. century. It was an amazing decade. In 1492 Christopher Columbus set sail for America. In that same year the King of Spain expelled all Jews from Spain on pain of death, bringing to an end centuries of Jewish culture in Spain, and causing a huge migration of dispossessed Jews through Europe, many of whom were welcomed by the Turkish sultan, who is reputed to have observed that the King of Spain had enriched Turkey by beggaring his own country.
At around the same time, at the court of the great banking family of the Medicis in Florence, Marsilio Ficino had established the Platonic Academy under the patronage of the Medicis and was translating the works of Plato. A bundle of manuscripts, lost for centuries and dating back to the 1st. and 2nd. centuries A.D. was discovered; this was the Corpus Hermeticum, a series of documents relating to Hermes Trimegistus, identical with the Egyptian god Thoth, god of wisdom. Cosimo de Medici told Ficino to stop translating Plato and to concentrate on the Corpus instead.
At the time it was believed that the Corpus really was the religion of the ancient Egyptians, and that Hermes was a kind of Egyptian Moses. The fact that they were written much later, and heavily influenced by Neoplatonism, had the effect of convincing readers at that time that Greek philosophy was founded on much older, Egyptian religious philosophy - this had a huge influence on liberal religious and philosophical thinking at the time. Into this environment came the Kabbalah, brought in part by fleeing Spanish Jews, and it was seized upon as another lost tradition, the inner, initiated key to the Bible.
Two figures stand out. One was Giovanni Pico, Count of Mirandola, who commissioned several
translations of Kabbalistic works, and did much to publicise Kabbalah among the intellectuals of the day. The other was Johannes Reuchlin, who learned to read Hebrew and became deeply immersed in Kabbalistic literature. It must be said that Jews were suspicious of this activity, finding that Christian scholars were using the Kabbalah as a bludgeon to persuade them to convert to Christianity.
It was out of this eclectic mixture of Christianity, Hermeticism, Neoplatonism, Kabbalah and
Renaissance humanism that Hermetic Kabbalah was born. Over the centuries it has developed in many directions, with strong influences from Freemasonry and Rosicrucianism, but continued input from Jewish Kabbalah has meant that many variants are not so different in spirit from the original. Its greatest strength continues to be a strong element of religious humanism - it does not attempt to define God and does not define what an individual should believe, but it does assume that some level of direct experience of God is possible and there are practical methods for achieving this. In a modern world of compartmentalised knowledge, scientific materialism, and widespread cultural and historical illiteracy, it provides a bridge between the spirit of enquiry of the Renaissance (the homo universalis or - in Hebrew - hakham kolel) and the emergence of a similar spirit of enquiry in our own time. (vialarp.org)
