The mechanism of evil eye can be explained according to the ancient and medieval theories of perception in natural terms. The damaging qualities of evil eye are caused by the bad qualities present in the person and are naturally affected onto his environment. Since all the senses operate essentially with the same principle, this happens not only through vision, but also through sounds (words), touch and smell. Accordingly the evil eye is often described in connection with infectious diseases (miasma theory). Only because the vision is the most noble, and “most of all the senses, makes us know and brings to light many differences between things” (Aristotle, Metaphysica, I.1.) are eye and vision highlighted in the context of fascination. All ancient theories of perception allow such affecting from long distance. This applies not only to the extramission (emission) theories of vision (what are usually mentioned in connection with the phenomenon of evil eye) but also some intromission theories of vision are able to account for the effects of evil eye. In the present article examples from Plutarchos, Aristotle, Roger Bacon, Peter of Limoges and others are employed to illustrate the principles. A central concept that emerges is the Aristotelian principle of eidos (in medieval times usually translated as species) what transmits qualities incorporeally to recipients. Every act of perception is in some way connected with the soul. Thus it is generally necessary forevil eye to operate, that direct contact between eyes is established, but in some cases it is also possible to damage the other even if the affected person does not herself have direct contact with the evil eye. This can happen when the evil qualities inside the fascinators soul are transmitted by other means (sound, smell, etc) or when the virtus visiva inside the eyes of the fascinator is extremely strong (as with the case of Triballi and the Illyrii described by Pliny). Another possibility is the extreme sensitivity (malleable soul) of the victim. As children and women are more sensitive than men usuallyevil eye is more dangerous to them. How qualities inside human soul are able to affect inanimate matter is illustrated with the example of red mirrors (Aristotle, De somniis 459b24ff). Such general understanding of fascination was in use till Early Modern times,when the phenomenon of evil eye become to be explained not any more by natural but supernatural means (demons).