We cannot blame God for the existence of evil
Someone may ask: “Why didn’t God get rid of the devil as soon as he deceived man in Paradise?” This was because of His great concern for us. If the devil had reigned by force, then there would be some grounds for this question. However, since he has been deprived of such power and was left only with the ability to persuade—and it is up to is if we choose to listen to him or not—why do you want to reject the opportunity to prosper and eliminate the cause for crowns? Even if God had allowed the devil to exist, knowing that he would be unbeatable and that he would defeat every single person, this still should not make you skeptical. It would still be up to us whether or not we allow the devil to prevail, and he would be unable to defeat anyone by force—only them who voluntary submit to him.
Additionally, if there are already many people who overcame his power, just as there are many who will defeat him in the future, why do you want to deprive these people (who will advance in virtue and attain a glorious victory) of such great honor? God allowed the devil to remain in order for man, who had been previously defeated by him, to vanquish him in turn. This will constitute the greatest hell possible for the devil and will bring upon him the worst condemnation.
If one continues with this type of reasoning, one will end up blaming and finding fault with God’s providence, and defaming God’s entire creation. One will criticize God for creating mouths and eyes; for human beings use their mouth to curse God and preach corruptive beliefs, and with their eyes they desire things which they shouldn’t and fall into adultery. Does this mean that God should have created people without a tongue and eyes? With this type of logic, we should also cut off people’s legs and sever their hands, since legs are used to race toward a variety of evils and hands are often covered in blood. Not even the ears can be spared from this savage syllogism, since they accept unbeneficial sounds and convey destructive teachings to the soul. Therefore, we should also cut off the ears. If this were to happen, then we must also do away with food, drinks, the sky and the earth, the moon and all the stars, along with all the genera of irrational animals. What would be the need for all this things if man, for whom they were all created, was cut to pieces and so pathetically dismembered?
Do you see how this lethal train of thought necessarily leads to a laughable and absurd conclusion? The devil does evil to and harms himself, not us. On the contrary, if we want, we can harvest innumerable good things on account of the devil—without, of course, him realizing or desiring this.
—St. John Chrysostomos