Select Works, Section 76

Section 1 1. Those enquiring whence Evil enters into beings, or rather into a certain order of beings, would be making the best beginning if they established, first of all, what precisely Evil is, what constitutes its Nature. At once we should know whence it comes, where it has its native seat and where it is present merely as an accident; and there would be no further question as to whether it has Authentic-Existence. But a difficulty arises. By what faculty in us could we possibly know Evil? All knowing comes by likeness. The Intellectual-Principle and the Soul, being Ideal-Forms, would know Ideal-Forms and would have a natural tendency towards them; but who could imagine Evil to be an Ideal-Form, seeing that it manifests itself as the very absence of Good? If the solution is that the one act of knowing covers contraries, and that as Evil is the contrary to Good the one act would grasp Good and Evil together, then to know Evil there must be first a clear perception and understanding of Good, since the nobler existences precede the baser and are Ideal-Forms while the less good hold no such standing, are nearer to Non-Being. No doubt there is a question in what precise way Good is contrary to Evil- whether it is as First-Principle to last of things or as Ideal-Form to utter Lack: but this subject we postpone.