EPICTETUS. DISCOURSES. Book iv. §11. 5-8.
THE first and highest purity, or impurity, then, is that which is formed in the soul. But you will not find the impurity of the soul and body to be alike. For what else of impurity can you find in the soul than that which renders it filthy with regard to its operations? Now the operations of the soul are its pursuits and avoidances, its desires, aversions, preparations, intentions, assents. What, then, is that which renders it defiled and impure in these operations? Nothing else than its perverse judgments. So that the impurity of the soul consists in wicked principles, and its purification in the forming right principles; and that is pure which hath right principles, for that alone is unmixed and undefiled in its operations.