The Enchiridion by St. Augustine
Chapter 96.--The Omnipotent God Does Well Even in the Permission of Evil.
Nor can we doubt that God does well even in the permission of what is evil. For He permits it only in the justice of His judgment. And surely all that is just is good. Although, therefore, evil, in so far as it is evil, is not a good; yet the fact that evil as well as good exists, is a good. For if it were not a good that evil should exist, its existence would not be permitted by the omnipotent Good, who without doubt can as easily refuse to permit what He does not wish, as bring about what He does wish. And if we do not believe this, the very first sentence of our creed is endangered, wherein we profess to believe in God the Father Almighty. For He is not truly called Almighty if He cannot do whatsoever He pleases, or if the power of His almighty will is hindered by the will of any creature whatsoever.