“Enq: Since Ammonius never committed anything to writing, how can one feel sure that such were his teachings?
Theo: Neither did Buddha, Pythagoras, Confucius, Orpheus, Socrates, or even Jesus, leave behind them any writings. Yet most of these are historical personages, and their teachings have all survived.
The disciples of Ammonius (among whom Origen and Herennius) wrote treatises and explained his ethics. Certainly the latter are as historical, if not more so, than the Apostolic writings.
Moreover, his pupils – Origen, Plotinus, and Longinus (counselor of the famous Queen Zenobia) – have all left voluminous records of the Philaletheian System – so far, at all events, as their public profession of faith was known, for the school was divided into exoteric and esoteric teachings.
Enq: How have the latter tenets reached our day, since you hold that what is properly called the WISDOM-RELIGION was esoteric?
Theo: The WISDOM-RELIGION was ever one, and being the last word of possible human knowledge, was, therefore, carefully preserved. It preceded by long ages the Alexandrian Theosophists, reached the modern, and will survive every other religion and philosophy.
Enq: Where and by whom was it so preserved?
Theo: Among Initiates of every country; among profound seekers after truth – their disciples; and in those parts of the world where such topics have always been most valued and pursued: in India, Central Asia, and Persia.”
H. P. Blavatsky
The Mark Of God: Understanding Your "I AM Presence" 