This paper aims at investigating the semantic value of the verb μαίνομαι “to rage, to be furious” in Homeric Greek, in order to clarify the striking semantic relationship between the common ‘irrational’ meaning of the verb and the original ‘rational’ meaning of the Indo European root *men “to think”, to which the verb traces back. The corresponding words for μαίνομαι in other Indo European languages (e.g. OInd. mányatē ; Av. mainyeite ; OIr. (do)moiniur ; OCS mъnjo ; Lit. miniu ) can be translated as “to think”, thus showing an opposite meaning. From a textual analysis of all the occurrences of μαίνομαι in the Iliad and the Odyssey, the study aims at finding semantic traces of the original meaning “to think” belonging to the Indo European r...