John records that the Ars notoria was especially attractive because he could not afford all the books needed for his studies, nor the many lectures. He seems to have abandoned his official course, wishing to take advantage of the promise of knowledge of all the sciences, and devoted himself to working with the Ars. He even used the Ars to teach his younger sister Latin and introduce her to magic. Gradually it became clear to John that the book hid invocations to demons within what appeared to be beautiful prayers. And yet, like any addict, John found it almost impossible to give up the Ars notoria completely; it was only when the visions became directly life-threatening that the Virgin, with St John the Evangelist as her intermediary, appeared and made it clear that, as John says, “the Ars notoria was deeply evil”.