This letter is a sweeping reconstruction of the figure known as Hermes Trismegistus, separating him from the mythological Egyptian Thoth and the Greek Hermes to reveal a distinct, quasi‑historical sage whose teachings shaped the entire Hermetic tradition. Hall begins by describing the catastrophic loss of ancient knowledge through the burning of the Alexandrian libraries, emphasizing how only fragments of Egypt’s sublime theology survive. He then traces the evolution of Hermes through Egyptian, Greek, Roman, and early Christian sources—showing how multiple historical figures, mythic attributes, and priestly lineages were gradually fused into the single archetype of “the Thrice‑Great.” Hermes emerges as a deified mortal: a philosopher‑king, scientist, priest, and lawgiver credited with founding writing, mathematics, astronomy, medicine, architecture, and sacred rites. Hall recounts legends of Hermes’ illumination, his ministry across Egypt, his final sermon, and the mysterious emerald tablet said to contain the core of Hermetic doctrine.

The second half of the letter explores the Hermetic philosophy itself, distinguishing the older, metaphysical Hermeticism from the later, alchemical reinterpretations. Hall outlines the cosmology of the Divine Pymander: the One Mind, the emanation of the planetary Governors, the formation of nature, and the descent of the primordial Man into the material world. Human redemption, in this system, is the ascent back through the seven planetary rings by purifying the soul of the qualities each planet bestowed. Hall then explains how, in the Middle Ages, Hermetic symbolism was misunderstood as literal chemistry, leading alchemists to search for physical gold, the elixir of life, and the philosopher’s stone—symbols that originally referred to wisdom, truth, and spiritual regeneration. He concludes by noting that the Rosicrucians and Paracelsians restored the deeper meaning of Hermeticism, preserving it as a doctrine of inner transformation rather than material transmutation.