Plato distinguishes two kinds of explanation: rational explanation of an agent’s practical reasoning leading to the selection of an action as a reasonable means to a good end, and dispositional explanation, given in terms of the agency that is such as to bring about an action of a given sort. Rational explanation seeks completion in the explainer’s recognition of the agent’s end as a good and the agent’s means as reasonable, which confers intelligibility on the action; dispositional explanation is a fallback when the explainer cannot see the agent’s end as good or means as reasonable—as is the case with evil. This claim is illustrated in Euripides’s and Seneca’s Medea plays.