I see nothing in this post that would answer my question. Why did God create Satan if he knew that Satan will turn evil?
Spock:
You may not find this a fully satisfactory answer to your question. But, at least it appears that you were not the first one to ask it. St. Thomas asked it as well and gave it lots of thought. After much thought, he recognized a couple of things: (1) that Satan and the demons, in all of the early literature and Scripture, looked to be inhabitants of lower realms, inclusive of earth. And, (2) from all of the earliest literature, sacred writings and Scripture, it appears that
good Angels were created with unshakable goodness. None were ever called on the carpet, or rebuked, or scolded - anywhere in any of the literature. And, this is so even of Satan and his followers.
How Satan and his followers embody evil is still an unanswered question, as Satan even now possesses the Angelic qualities of perfection determinant of Angels. St. Thomas explains that an Angel is created in a state of Perfection, and that perfection cannot be altered so long as that Angel remains in his realm. But, God brought all of the Angels up into the higher realm, the Vision realm, with himself. There an Angel could choose to reject being there, as they were given free will. Some Angels, like Satan, chose to remain in the lower realm.
In the lower realm - the angelic realm, which extends from the bottom of the Vision realm down to include the Earth, the
fallen Angels chose to remain. There, they could not duplicate God, for even they know that is impossible, instead they were so enamored with their own self-glory that the delight they enjoyed in themselves was enough to cause them to err in their thinking. Satan committed to this lower realm of existence. He and his followers were thus cast down to these lower realms, which includes the angelic realm and the earthly realm.
That is why the Earth is included in Satan’s territory. Once an Angel is created, that Angel remains in existence from then on. He has a beginning but no ending. He has been cast out of the realm called the Vision, but is permitted to exist in the lower realms. Notwithstanding all his power and strength, the human soul has been given more than enough strength and power to not only resist his enticements, but also, to vanquish him from our hearts. The people of Earth are here for the purpose of replacing Satan and the fallen Angels who were cast out of the realm of the Vision. Only the elect will be allowed into the realm of the Vision. (I am planning to be one of those elect - I hope.)
I spent much of the holidays researching this subject because I knew it was important to you. The best explanation may be found in
The Teaching of the Catholic Church, Vol I, chap VIII, The Angels.
God bless,
jd