I have had many discussions with Calvinists and it seems that their commitment to the idea of immutability is tied to their view of goodness. They can't imagine any kind of being as good unless the option to do evil is taken away. So they say that God's nature is fixed to only do good without any ability to do evil.
I've offered up to Calvinists the possibility that God is good, not because He is unable to do evil, but because He freely chooses to do the right thing for its own sake. That usually sends a Calvinist into orbit, because they believe that if you have the option to do evil, then you are evil. So they then accuse me of attacking God's goodness. But what I am doing is just trying to make God's goodness meaningful.
Wayne Grudem wrote in his Systematic Theology about the importance of the doctrine of Immutability. He states that if God actually had the free will to choose between the right and wrong thing, then He would probably become completely evil and turn into the devil himself.
But, when we watch a movie where the hero is faced with some moral dilemma and they end up choosing to do what's right, we rejoice. But it seems the Calvinist should jeer, because for someone to even have the ability to choose between good and evil is intrinsically evil.
But it seems to me that mankind has an innate understanding that good character doesn't come from a fixed predisposition to only do the thing that you are able to. It's generally understood that you can't rightly judge people as good or evil based on fixed attributes of their nature like their skin color, height, or gender. We judge people based on their character which is determined by the freely chosen moral decisions that they make.
Can morality, righteousness, goodness, etc. really exist without free moral ability? Of course not.
