Malignant Magnetism.--As a number of persons are likely to fear such evil influence of others upon them, the question of the possibility of it must come up for discussion in order that its status may be clear in the physician's mind, for by just as much as he can make certain to the patient that modern psychology refuses to accept distant influence, will he be able to reassure his patient. Of course, the patients who come with such complaints have usually some element of mental trouble. The alienist sees any number of people who are sure that enemies at a distance are working spells upon them, some by electrical, some by magnetic means, and some by telepathic absent treatment, or absent ill-wishing. Such notions are the delusions of the disequilibrated and these persons often cannot be reasoned with. Yet very often a distinct delusion may be reasoned out of even a subrational person, if it is taken seriously, and some striking expression of its irrationality and of its total disagreement with scientific views can be shown to the patient. Action Without a Medium.--The medieval scholastic philosophers quoted as an absolutely accepted principle the Latin axiom, _"actio in distans repugnat."_ Literally translated this means action at a distance is repugnant to reason. Expressed less technically, the principle declares that any action of one body on another, where there is no medium connecting them, no link that in some way places them in contact with one another, is absurd. The expression _in distans_ means that the two bodies are separated from one another and stand in two places having no connection of any kind. This principle would ordinarily seem to preclude the possibility of one person acting on another, unless there is some mode of communication.