As it is right that we should know the causes of good and evil, so much of them at least as will suffice for the way that leads us to the kingdom, where there will be life without the shadow of death, truth without any alloy of error, and happiness unbroken by any sorrow, I have discussed these subjects with the brevity which my limited space demanded. And I think there cannot now be any doubt, that the only cause of any good that we enjoy is the goodness of God, and that the only cause of evil is the falling away from the unchangeable good of a being made good but changeable, first in the case of an angel, and afterwards in the case of man.
Reproduced in full. Translation: Nicene and Post-Nicene Fathers, series 1, vol. 3 (Schaff, 1887), public domain (Public domain).