But why does the existence of the Principle of Good necessarily comport the existence of a Principle of Evil? Is it because the All necessarily comports the existence of Matter? Yes: for necessarily this All is made up of contraries: it could not exist if Matter did not. The Nature of this Kosmos is, therefore, a blend; it is blended from the Intellectual-Principle and Necessity: what comes into it from God is good; evil is from the Ancient Kind which, we read, is the underlying Matter not yet brought to order by the Ideal-Form.
But, since the expression “this place” must be taken to mean the All, how explain the words “mortal nature”? The answer is in the passage [in which the Father of Gods addresses the Divinities of the lower sphere], “Since you possess only a derivative being, you are not immortals… but by my power you shall escape dissolution.” Ennead I,8,7