┌─╷─┐ ╵┌┼┐╵ polyphanes.smol.pub ╷└┼┘╷ by polyphanes └─╵─┘
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No, "ceremonial magic" (empty as the term is—most magic and religion is ceremonial in nature, come on) is not a closed practice. It was never closed, and it was never considered closed by anyone actually involved with it. By all means, have at some yoga, but claiming that it's closed is a goddamn stretch. Like, there are no initiated mysteries in "ceremonial magic" that you don't already get from just doing things, maybe with someone more experienced than you to train under, but even then they're not someone who has to somehow "ordain" or "initiate" you.
When most people say "ceremonial magic", they generally refer to Solomonic magic, the texts of which are based on the myth of Solomon summoning and binding demons. It's been learned from books by literally anyone who can get their hands on it—and this sort of stuff has literally been in publicly-circulated books since well before the printing press. To that end: can you read? Can you follow instructions? Do you want to do it? Congratulations, you fulfill all the cultural and educational requirements necessary to do Solomonic magic—and, by extension, basically all its variant offshoots. Sure, Hebrew script and words are often part of Solomonic magic, sometimes because part of it comes from Jewish magical practices (which in this case are also definitely not closed), sometimes because of Orientalizing impulses to make shit seem more mystical; big whoop. Besides, many of those words written in Hebrew aren't actually Hebrew at all, but back-transliterations of Greek words or imports from Christian or other cultural influences into Solomonic magic that weren't Jewish at all to begin with. Even the named angels like Michael, Raphael, Gabriel, et al. aren't (either entirely or partially) Jewish in origin, only appearing after the Babylonian Exile and showing definite pagan influences. This only increases, especially with pagan and non-Abrahamic origins of many spirits associated with goetia.
Not to belabor the point, but let me repeat myself to make my point clear: "ceremonial magic" is not closed. To say it's closed is wrong and shows a gross misunderstanding of what "closed" actually means. Especially when people conflate Solomonic magic with Jewish religious practices, saying this kind of nonsense recklessly comes across as racist, xenophobic, and hateful. What, are people really gonna claim that only Jewish people have ceremonies? That only Jews can summon demons using spooky words? If not Jews, then who the hell would ceremonial magic even be closed for or by? Renaissance Italian translators of Hebrew and Arabic manuscripts? (No.)
To be sure, even in our modern day, while there are traditions like the Golden Dawn, the A∴A∴, and others that are closed and require initiation to belong to and practice with as specific organizations and traditions, but they're traditions that make use of "ceremonial magic" and not the be-all-end-all of it. Outside of doing practices specific to those limited contexts, if you want to go to Esoteric Archives, pick up a grimoire, and start putting it to use, there is literally nobody who can actually tell you "no". Let me make it easy for you: as someone who does "ceremonial magic", as someone who can be considered a "ceremonial magician", you have my express permission and license to do "ceremonial magic". Have at, have fun, God and gods speed you.