Note 164 — Chapter V · Belief in Magic in the Empire

Stromata, bk. v, ch. 9. Nor was such mysticism advocated by theological writers alone. Roger Bacon—but one instance from many—declared that one lessened the majesty of knowledge who divulged its mysteries, and even went to the length of enumerating seven methods by which the arcana of philosophy and science might be concealed from the crowd (a vulgo), De Secretis Artis et Naturae et de Nullitate Magiae. Rolls Series, vol. xv, pp. 543–544.