XI. OF THE FALL OF THE BAD ANGELS
Did all the angels make the choice deserving of heaven offered to them by God?
No,for some of them turned away from God (LXIII. 3).
Why did certain angels refuse to turn to God?
Because they were prompted through pride and through the desire of self-sufficiency making themselves like unto God (LXIII. 2, 3).
Was this pride a great sin?
Yes, it was a heinous sin which provoked God's anger on the instant.
What was the result of God's just anger in regard to this sin of the angels?
On the instant God cast the bad angels into hell; and this place will be for ever the scene of their punishment (LXIV. 4).
What are these bad angels who revolted against God and were cast into hell called?
They are called the devils (LXIII. 4).
(Next - XII. OF THE CREATION OF MATERIAL SUBSTANCES, AND THE WORK OF THE SIX DAYS)
Pegues OP, R P Thomas. Catechism of the "Summa Theologica" of Saint Thomas Aquinas for the Use of the Faithful ((pp. 55-57)). Veritatis Splendor Publications. Kindle Edition.