Why God Did Not Destroy Satan
God could employ only such means as were consistent with truth and righteousness. Satan could use what God could not—flattery and deceit. It was therefore necessary to demonstrate before the inhabitants of heaven and all the world that God's government is just, His law perfect. Satan had made it appear that he himself was seeking to promote the good of the universe. The true character of the usurper must be understood by all. He must have time to manifest himself by his wicked works.EP 14.2
All evil he declared to be the result of the divine administration. It was his own object to improve upon the statutes of God. Therefore God permitted him to demonstrate the nature of his claims, to show the working out of his proposed changes in the divine law. His own work must condemn him. The whole universe must see the deceiver unmasked.EP 14.3
Even when Satan was cast out of heaven, Infinite Wisdom did not destroy him. The allegiance of His creatures must rest upon a conviction of His justice and benevolence. The inhabitants of heaven and of the world could not then have seen the justice of God in the destruction of Satan. Had he been immediately blotted out of existence, some would have served God from fear rather than from love. The influence of the deceiver would not have been fully destroyed, nor would the spirit of rebellion have been utterly eradicated. For the good of the entire universe through ceaseless ages he must more fully develop his principles, that his charges against the divine government might be seen in their true light and that the justice of God and the immutability of His law might be forever placed beyond question.EP 15.1
Satan's rebellion was to be a lesson to the universe through all coming ages—a perpetual testimony to the nature of sin and its terrible results. Thus the history of this experiment of rebellion was to be a perpetual safeguard to all holy beings to prevent them from being deceived as to the nature of transgression.EP 15.2
“His work is perfect; for all His ways are judgment: a God of truth, and without iniquity, just and right is He.” Deuteronomy 32:4.EP 15.3