The god Thoth fascinated the Greeks, who identified him with their messenger god Hermes, and gave him the epithet Trismegistus, meaning "thrice-great." The Greeks were particularly captivated by the elusive Book of Thoth, described by Clement of Alexandria as forty-two secret books of wisdom. These texts, housed in temple archives, were regarded as the work of Thoth himself.

These books were in fact rewritten as the Hermetica by Graeco-Roman visitors during the Ptolemaic and Roman periods, from the first to the third centuries AD, and so contained a mix of Egyptian myth and Greek philosophy, with the addition of alchemical and astrological lore and powerful spells. Many believed the texts to be immeasurably ancient, and steeped in Egyptian wisdom that had been passed down through the millenia from one initiate to another. To their adherents, the writings of Hermes Trismegistus (Thoth) amounted to nothing less than the universal secret of life. The Hermetica included elaborate spells for imprisoning daemons, and magickal charms to make statues speak or prophesy, as well as tets on classical subjects such as astronomy, medicine, geography, and even rudimentary chemistry. These were treated in a philosophical language that was mostly taken from contemporary Greek thinking but was widely believed to be far older. Throughout the Middle Ages, the books, appealed enormously to scholars and alchemists from all traditions-Muslims and Jews as well as Christians. For example, the Polish astronomer Copernicus, who established that the earth orbited the sun, cliamed that he had reached his conclusions partly as a result of his studt of Hermetic writings.