That is a rather bizarre and unsubstantiated date. Even if you believe modern paganism is no older than Gerald Gardner’s creation, 1946 would be a more probably date, when he had clearly become active in leading a coven, or perhaps 1954, when he went public with his book Witchcraft Today. It’s more reasonable to trace modern paganism to occult movements and nature/woodcraft groups which were already quite active in the years before World War I and as early as the 1890s. They in turn derived much of their material from occultists in the 1840s, the masonic traditions dating back to the 1700s and occult traditions dating to the high middle ages. It is also accurate to say that the roots of paganism, if not the specific ritual forms, date their founding to the beginnings of human awareness and the earliest hunter-gatherer cultures - ie 50,000 B.C.
The whole game supposes that antiquity is a relevant factor in judging a religion’s legitimacy. Slavery is a lot older than any religion, but we don’t say that makes it respectable. Christianity, and even Judaism, by contrast, came along quite late in the timeline of human evolution.
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