3. The best rule in any government is to provide for everything under government according to the mode of its nature: just administration consists in this. As then it would be contrary to any rational plan of human administration for the civil government to debar its subjects from acting according to their offices and conditions of life, except perhaps in an occasional hour of emergency, so it would be contrary to the plan of divine government not to allow creatures to act according to the mode of their several natures. But by the very fact of creatures so acting there follows destruction and evil in the world, since by reason of mutual contrariety and inconsistency one thing is destructive of another.*
5. There are many good things in creation which would find no place there, unless evils were there also. Thus there would be no patience of the just, if there were not the malice of persecutors: no room for vindictive justice, if there were no offences: and in the physical order one thing cannot come to be unless something else is destroyed.* If then evil were wholly excluded from the universe by divine providence, the number of good things would be proportionally diminished: which ought not to be, because good is more vigorous in goodness than evil in badness (virtuosius est bonum in bonitate quam in malitia malum), as above shown (Chap. XII).
6. The good of the whole takes precedence of the good of the part. It belongs then to a prudent ruler to neglect some defect of goodness in the part for the increase of goodness in the whole, as an architect buries the foundation under the earth for the strengthening of the whole house. But if evil were removed from certain portions of the universe, much perfection would be lost to the universe, the beauty of which consists in the orderly blending of things good and evil (pulcritudo ex ordinata bonorum et malorum adunatione consurgit), while evil things have their origin in the breaking down of good things, and still from them good things again take their rise by the providence of the ruler, as an interval of silence makes music sweet.
7. Other things, and particularly inferior things, are ordained to the end of the good of man. But if there were no evils in the world, much good would be lost to man, as well in respect of knowledge, as also in respect of desire and love of good: for good is better known in contrast with evil; and while evil results come about, we more ardently deire good results: as sick men best know what a blessing health is.
Therefore it is said: Making peace and creating evil (Isai. xlv, 7): Shall there be evil in the city that the Lord has not done? (Amos iii, 6.)
Boethius (De consolatione, Lib. I, prosa 4) introduces a philosopher asking the question: 'If there is a God, how comes evil?'. The argument should be turned the other way: 'If there is evil, there is a God.' For there would be no evil, if the order of goodness were taken away, the privation of which is evil; and this order would not be, if God were not.
Hereby is taken away the occasion of the error of the Manicheans, who supposed two primary agents, good and evil, as though evil could not have place under the providence of a good God.
We have also the solution of a doubt raised by some, whether evil actions are of God. Since it has been shown (Chap. LXVI) that every agent produces its action inasmuch as it acts by divine power, and that thereby God is the cause of all effects and of all actions (Chap. LXVII); and since it has been further shown (Chap. X) that in things subject to divine providence evil and deficiency happens from some condition of secondary causes, in which there may be defect; it is clear that evil actions, inasmuch as they are defective, are not of God, but of defective proximate causes; but so far as the action and entity contained in them goes, they must be of God, -- as lameness is of motive power, so far as it has anything of motion, but so far as it has anything of defect, it comes of curvature of the leg.
3.70 : How the Same Effect is from God and from a Natural Agent
3.72 : That Divine Providence is not inconsistent with an element of Contingency in Creation