The dominant opinion nowadays is that the omnipotence of God is like the absolute power of a monarch in the world, who can do whatever she or he wishes on a whim: absolve and condemn at will, make the guilty innocent, declare the unfaithful to be faithful, promote undeserving and unworthy people above those who are worthy and deserving. Under any pretext whatever, he or she can even seize citizens’ assets, sentence them to death, and so on.
Through this ridiculous opinion, belief, and teaching about divine omnipotence, the same number of falsities, errors, and fabled monsters have poured into the church as there are movements, branches, and new sects of the faith. There is still room for more—as many more as the jars you could fill with water from a great lake, or as many as the snakes in an Arabian desert that could crawl out of their caves to enjoy basking in the sunshine. All you would need [to start a new movement, branch, or sect] are those two little words, “omnipotence” and “faith,” and a program to spread enough conjectures, fables, and blithering to be physically stimulating.
Each of those two words pushes reason aside. Once our reason is disengaged, our thought process is no better than that of a bird flying overhead. What then becomes of the spiritual aspect that we have but animals lack? It becomes like the smell in a zoo: it suits the wild animals that are there but does not suit people unless they are particularly beastly.
If divine omnipotence extended to doing evil as well as good, what difference would there be between God and the Devil? They would be no different than two rulers, one of whom is a monarch and also a tyrant, while the other is a tyrant whose power has been curtailed so that he or she cannot be called a monarch anymore. They would be no different than a shepherd who is allowed to keep a sheep and a leopard, and another shepherd who is not allowed to do the same. Surely anyone can see that good and evil are opposites, and that if God by his omnipotence were able to will and do both good and evil, he could do absolutely nothing. He would have no power at all, much less omnipotence.
This situation would be much like the way two wheels going in opposite directions act against one another, causing each wheel to come to a stop. It would be like a ship whose course ran against a strong current in the opposite direction. If the ship did not drop anchor and stay still, it would be carried off to its doom. It would be like a human being with two wills that disagreed with each other. When one of them acted, the other would have to be still. Otherwise, if both acted at once, a dizzying madness would assault the mind.
from True Christianity, Section 57