The good, by a free choice, was the cause of evil and remains its substratum. Fallen angels and humans, as creatures, are and remain good and exist from moment to moment only by and in and for God. And, just as sin is dependent on the good in its origin and existence, so it is in its operation and struggle. It has the power to do anything only with and by means of the powers and gifts that are God-given. Satan has, therefore, correctly been called the ape of God. When God builds a church, Satan adds a chapel. Over against a true prophet, he raises up a false prophet. Over against Christ, he poses the Antichrist. Even a band of robbers can only exist if, within its own organization, it respects the rules. A liar always garbs himself or herself in the guise of truth. A sinner pursues evil under pretense of the good. Satan himself appears as an angel of light. In its operation and appearance, sin is always doomed to borrow, despite itself, from the treasury of virtue. It is subject to the unalterable fate – while striving for the destruction of all good – of working simultaneously on its own demise. It is a parasite of the good.
From: Reformed Dogmatics: Volume 3: Sin and Salvation in Christ by Herman Bavinck; translated from the Dutch by John Vriend (Grand Rapids: Baker Academic, 2006), p. 139. The translation is from the second Dutch edition of 1910.