Human prosperity was supposed to be especially provocative of the envy of evil spirits, and their method of retaliation was to strike back through a human agency and by the technique of the evil eye. The Koran contains a whole chapter devoted to the evil eye.  And intelligent human beings still believe in good luck, the evil eye, and astrology.  The whole phallic cult grew up as a defense against the evil eye. 
Many primitive peoples believed the soul looked out upon the world through human eyes; therefore did they so cravenly fear the malevolence of the evil eye.  Primitives thought much sickness caused by evil eye.  The monotheists keep their subordinate gods as spirits, demons, fates, Nereids, fairies, brownies, dwarfs, banshees, and the evil eye.