 In this letter Arrian stated that the "Enchiridion" was selected from the "Discourses of Epictetus" according to what he considered to be most useful, most necessary, and most adapted to move people's minds.Around half of the material in the "Enchiridion" has been shown to have been derived from the surviving four books of "Discourses" but variously modified.Other parts are presumed to be derived from the lost "Discourses".