Grimassi shares in common, in his books, the general "Witch-cult hypothesis" that appears in the writings of Charles G. Leland (Aradia, or the Gospel of the Witches, 1899), a theory to the effect that European witchcraft was the continuation of an ancient pre-Christian form.
Grimassi writes that Aradia di Toscano passed on a religion of witchcraft, based on ancient Etruscan paganism, to her followers (whom Grimassi calls "The Triad Clans").