How could a look of envy be a weapon of annihilation of the body of the envied person? This case of action at a distance led medieval scholars to formalise a certain type of relationship between emotion (personally experienced) and destruction (of the other). The article examines the sources of scholastic reasoning on fascination / evil eye, namely Avicenna and Algazel, Ancient literature, Medieval encyclopedias and Salernitan texts. Then it studies the 13th- to 15th-century doctrinal constructions that explore the relationship between the evil eye and envy. Two complementary perspectives are identified: a psychological-theological way that emphasizes the harmful effects of envy from a pastoral point of view, without explaining how the passions of the soul can have an effect on external bodies, and a naturalist way, inspired by medical literature, that explains the action at a distance of the fascinator’s soul according to the pattern of the spread of diseases by contagion.