Hermeticism or Hermetism is a philosophical system based on the purported teachings of Hermes Trismegistus (a legendary Hellenistic combination of the Greek god Hermes and the Egyptian god Thoth). These teachings are contained in the various writings attributed to Hermes (the Hermetica), which were produced over a period spanning many centuries (c. 300 BCE – 1200 CE) and may be very different in content and scope.

The Corpus Hermeticum is a collection of 17 Greek writings whose authorship is traditionally attributed to the legendary Hellenistic figure Hermes Trismegistus, a syncretic combination of the Greek god Hermes and the Egyptian god Thoth. The treatises were originally written between c. 100 and c. 300 CE, but the collection as known today was first compiled by medieval Byzantine editors. It was translated into Latin in the 15th century by the Italian humanist scholars Marsilio Ficino (1433–1499) and Lodovico Lazzarelli (1447–1500).

The Kybalion is a book originally published in 1908 by "Three Initiates" (often identified as the New Thought pioneer William Walker Atkinson, 1862–1932) that purports to convey the teachings of Hermes Trismegistus.

While it shares with ancient and medieval Hermetic texts a number of traits such as philosophical mentalism, the concept of 'as above, so below', and the idea that everything consists of gendered polar opposites, as a whole it is more indebted to the ideas of modern occultist authors, especially those of the New Thought movement to which Atkinson belonged. A modern Hermetic tract, it has been widely influential in New Age circles since the twentieth century. Contents: The Kybalion - 1912 by The Three Initiates (William Walker Atkinson) Corpus Hermeticum - Treatises written between c. 100 and c. 300 Common Era by Hermes Trismegistus and translated in 1906 by G. R. S. Mead The Emerald Tablets of Thoth the Atlantean - 1925 by M. Doreal The Life and Teachings of Hermes Trismegistus - Manly P. Hall 1928