Ancient Greek: Ἑρμῆς ὁ Τρισμέγιστος, “thrice-greatest Hermes”; Latin: Mercurius ter Maximus) is the purported author of the Hermetic Corpus, a series of sacred texts that are the basis of Hermeticism. Hermetic ancient universal wisdom .
He may be a representation of the syncretic combination of the Greek god Hermes and the Egyptian god Thoth. In Hellenistic Egypt, the Greeks recognised the congruence of their god Hermes with Thoth. Subsequently the two gods were worshipped as one in what had been the Temple of Thoth in Khemnu, which the Greeks called Hermopolis.
Both Thoth and Hermes were gods of writing and of magic in their respective cultures. Thus, the Greek god of interpretive communication was combined with the Egyptian god of wisdom as a patron of astrology and alchemy. In addition, both gods were psychopomps; guiding souls to the afterlife. The Egyptian Priest and Polymath Imhotep had been deified long after his death and therefore assimilated to Thoth in the classical and Hellenistic period.
Another good description :
ALL Consciousness . HERMES TRISMEGISTUS, “the thrice greatest Hermes.” The name given by the Greeks to the Egyptian god Thoth or Tehuti, the god of wisdom, learning, and literature. Thoth is alluded to in later Egyptian writings as “twice very great” and even as “five times very great” in some demotic or popular scripts.–ca. third century B.C. To him was attributed as “scribe of the gods” the authorship of all sacred books which were thus called “Hermetic” by the Greeks. These, according to Clemens Alexandrinus, were forty-two in number and were sub-divided into six portions, of which the first dealt with priestly education, the second with temple ritual, and the third with geographical matter. The fourth division treated of astrology, the fifth of hymns in honor of the gods and a text-book for the guidance of Kings, while the sixth was medical. It is unlikely that these books were all the work of one individual, and it is more probable that they represent the accumulated wisdom of Egypt, attributed in the course of ages to the great god of wisdom.
As “scribe of the gods” Thoth was also the author of all strictly sacred writing. Hence by a convenient fiction the name of Hermes was placed at the head of an extensive cycle of mystic literature, produced in post-Christian times. Most of this Hermetic or Trismegistic literature has perished, but all that remains of it has been gathered and translated into English. It includes the “Poimandres”–virgin of the world–, “the Perfect Sermon,” or the “Asclepius” excerpts by Stobacus, and fragments from the church fathers and from the philosophers, Zosimus and Fulgentius. Hitherto these writings have been neglected by theologians, who have dismissed them as the offspring of third century Neo-Platoism. According to the generally accepted view they were eclectic compilations, combining neo-Platonic philosophy, Philonic Judaism and Kabalistic theosophy in an attempt to supply a philosophic substitute for Christianity. The many Christian elements to be found in these mystic scriptures were ascribed to plagiarism. By an examination of early mystery writings and traditions it has been proved with some degree of certainty that the main source of Trismegistic Tractates is the wisdom of Egypt, and that they “go back in an unbroken tradition of type and form and context to the earliest Ptolemaic times.”
The “Poimandres,” on which all later Trismegistic literature is based, must, at least in its original form, be placed not later than the first century. The charge of plagiarism from Christian writings, therefore, falls to the ground. If it can be proved that the “Poimandres” belongs to the first century, we have in it a valuable document in determining the environment and development of Christian origins.