Mystical wisdom that, together with the Kabbalah, formed the foundation of Western occultism. The term is derived from the surviving fragments of a multi-volume work known as the Corpus Hermeticum, or Hermetica. This mystical philosophical work was allegedly written by Hermes Trismegistus ('Thrice-Greatest') a mythical composite of the Egyptian god Thoth and the Greek god Hermes. The fragments present a synthesis of Kabbalistic, Neo-Platonic and Christian mystical and spiritual traditions.
According to legend, the Hermetic books were written on papyrus and stored in one of the great libraries in Alexandria. Most were lost when the library burned. Surviving fragments supposedly were buried in a secret desert location known only to select initiates.
Controversy over the age and authorship of the Hermetica has existed since at least the Renaissance. Isaac Casaubon (1559-1614), French classical scholar and theologian, claimed that the works were not of Egyptian origin but were written by early Christians or semi-Christians. Casaubon's exegesis helped to bring about a decline in the Renaissance interest in magic.
In all likelihood, the Hermetic works were written even later than Casaubon believed, by multiple anonymous authors who used the pseudonym 'Hermes Trismegistus'.