Brett explains that there are indeed some things that God can not and would not do.
We certainly want to affirm that God is all-powerful. The question we must ask is: What does it mean for God to be all-powerful?
God is all-powerful, so He can do all that power can do. He is limited to what power is able to do. What does that mean? There are limits to what He can do within His nature. When we say He’s all-powerful, we mean his power is vast. He certainly can do more than any human can do. What limits his power is his nature.
There is no one Greater than God because he can do all that power can do. Sometimes Christians get nervous when saying that God is limited, but certainly He’s limited by his nature. How does that work? Can God sin? No, of course not. Why? Because of his nature. God is morally perfect and holy, so He can’t sin. That’s an example of a limit on what God can do. Of course, that doesn’t count against God.
Can God create a square circle? A married bachelor? Of course not. These are logical impossibilities. God cannot do that which is absurd. God is limited by his rational nature. The laws of logic are not merely human creations; they flow from God’s nature.
God is limited by His nature. That includes His perfect moral nature and His rational nature. God is all-powerful in that He can do anything that is consistent with His nature.