 Albertus Magnus rejects Avicenna’s long-distance theory because it breaks with the Aristotelian rule that there is no efficient causation without material contact (De sensu et sensato 1.10). Thomas Aquinas follows a third alternative: that psychic powers can move the intervening medium, and so indirectly act on external objects, which explains the damage caused by an evil eye. Thomas borrows from a passage in Aristotle’s On Dreams, in which air is moved and affected by the eyes of menstruating women (459b23–60a24). True miracles, however, are always produced by God (Summa theol. Ia q.117 a. 3). In the later Middle Ages, the Aristotelian theory of the movable medium proved more successful than the extramission and action-at-a-distance theories of al-Kindī and Avicenna. An exception is Roger Bacon, who teaches that some persons are able to send out “powers, forms, and heat” in order to alter bodies outside. Bacon employs al-Kindī’s theory of extramission in order to explain magic as a purely natural phenomenon (in De secretis operibus artis et naturae).