Despite his previous declaration that he need not discuss the _pythonici_, John now proceeds to do so, listing instances of ambiguous and deceptive Delphic oracles and discussing at length the well-worn subject of Saul and the witch of Endor. He concludes the chapter by a warning against abuse of the practice of exorcism: “For such is the slyness of evil spirits that what they do of their own accord and what men do at their suggestion, they with great pains disguise so that they appear to perform it unwillingly. They pretend to be coerced and simulate to be drawn out as it were by the power of exorcisms, and that they may be the less guarded against they compose exorcisms apparently expressed in the name of God or in the faith of the Trinity or in the power of the incarnation or passion; and they transmit the same to men and obey men who use these, until they finally involve them with themselves in the crime of sacrilege and penalty of damnation. Sometimes they even transform themselves into angels of light, they teach only things of good repute, forbid unlawful things, strive to imitate purity, make provision for needs, so that, as if good and favoring, they are received the more familiarly, are heard the more kindly, are loved the more closely, are the more readily obeyed. They also put on the guise of venerable persons....”[491] [Sidenote: Divination from polished surfaces.] “The _specularii_,” John continues, “flatter themselves that they immolate no victims, harm no one, often do good as when they detect thefts, purge the world of sorceries, and seek only useful or necessary truth.”[492] He insists that the success of their efforts is none the less due to demon aid. John tells how as a boy he was handed over for instruction in the Psalms to a priest who turned out to be a practitioner of this variety of magic, who after performing various adjurations and sorceries tried to have John and another boy look into polished basins or finger-nails smeared with holy oil or chrism and report what they saw. The other boy saw some ghostly shapes but John thanks God that he could see nothing and so was not employed henceforth in this manner. He adds that he has known many _specularii_ and that they have all suffered loss of their sight or some other evil except the aforesaid priest and a deacon, and that they took refuge in monasteries and later suffered evils above their fellows in their respective congregations. [Sidenote: Natural science and medicine.]