For a century and a half after Ficino, the idea that there was a Perennial Philosophy [the idea that “[a]ll religions shared a common origin in a single perennial (or primeval or primordial) religion that had subsequently taken a variety of forms, including the Zoroastrian, Phara- onic, Platonic, and Christian”] became increasingly widely accepted. Perennialism was, however, discredited in the early seventeenth century and thereafter survived only at the edges of Western intellectual life. Then, in the nineteenth century, Perennialism was revived in a slightly modified form, with the newly discovered Vedas being taken as its surviving textual expression. It was in this form, as we shall see, that Guénon encountered Perennialism, and it is this form of Perennialism that is advanced in the Introduction générale, was rejected by [indologist Sylvain] Lévi, and is central to the Traditionalist philosophy. [This element is “what may be called Vedanta-Perennialism”.]
[…]
The principal importance of these two books [ Le Théosophisme, histoire d’une pseudo-religion (1921) & L’erreur spirite (1923)] for the Traditionalist philosophy is that they advanced two interrelated concepts, “counterinitiation” and “inversion.” In Traditionalist use, “counterinitiation” is the opposite not of initiation as such but of initiation into a valid, orthodox tradition such as that represented by Vedanta. “Counterinitiation” is initiation into pseudo-traditions such as Theosophy, which are in fact the inversion of true tradition. Instead of leading to the Perennial Philosophy, counterinitiation leads away from it. The place of initiation in the Traditionalist philosophy (the third of the three central elements) is considered later.
More important than “counterinitiation” is the related concept of “inver- sion.” Gue ́non did not invent this concept, which is present in eschatological accounts of the Anti-Christ (who is the inversion of the true Christ), but it was to become a major element of Traditionalism. Counterinitiation is the inversion of initiation, but inversion is not restricted to questions of initiation. In its fully developed Guénonian form, inversion is seen as an all-pervasive characteristic of modernity. While all that really matters is in fact in decline, people foolishly suppose that they see progress.
Inversion, the second concept advanced in these two books, is one of the most powerful elements in the Traditionalist philosophy, providing many readers of Guénon and of later Traditionalists with a persuasive explanation of much that seemed most perplexing to them about the twentieth century. To take contemporary examples, phenomena that can be explained as examples of inversion include youth fashions of apparent ugliness, the preaching of the values of “letting it all hang out” as superior to self-restraint, the existence of pedophile priests, and the photographs of Andres Serrano. In the words of a contemporary Traditionalist — a young and talented European scholar of Islam — once the modern world is understood in terms of decline rather than progress, almost everything else changes, and there are not many people left you can usefully talk to. Of course, a non-Traditionalist might point out that comparable examples of inversion could be found in the fifteenth century as well as the early twenty-first century, but that is not the point.
– Against the Modern World: Traditionalism and the Secret Intellectual History of the Twentieth Century (2004), pp. 24-5
Immediately on joining the Theosophical lodge Isis in Paris, Guénon’s first master [Gérard] Encausse began to write in a French Theosophical journal — Le Lotus, revue des Hautes Etudes Théosophiques — not so much on Theosophy as on his other main interest, initiation, which is the third major element in the Traditionalist philosophy. According to Encausse, while Theosophy was transmitting initiations from India, where “the ancient truth still survives,” contemporary Freemasonry had allowed political and material interests to drive out spiritual ones, even though its rituals derived from ancient initiations. This, in slightly modified form, became the Traditionalist conception of initiation.
In general, initiation has two aspects, which can be described as exoteric and esoteric. The classic Christian initiation is baptism. Its exoteric significance is to mark one’s entry into the Christian community, while (in Catholic theology) the esoteric significance is that it gives the new Christian access to divine grace, and so to the possibility of salvation, which is otherwise absent. It was the esoteric aspects of non-Christian initiations such as Masonic ones that interested Encausse, and so (later) Guénon and the Traditionalists.
Ibid., p. 45