Can God make a rock which He can not lift?
A) God exists
B) God is omnipotent
If God can or cannot create a rock which He cannot lift, then either Axiom A or B is apparently
incorrect. For if God is able to create the rock; He will limit his power in doing such. If God isn't able to create the rock then Axiom B is falsified.
In order for Axiom B to be correct; God must be able to do all i.e. create the rock which He cannot lift, create a rock and lift it (it is thus not defined as "rock which He cannot lift"), or not create the rock at all. Indeed Axiom B assumes all these things true. Thus, we can observe that the omnipotent God has a choice.
Observe that in the inferences I said "For if God is able to create the rock; He will limit his power in doing such". Notice now that the conclusion of the premise is in past tense. Axiom B says that God is
omnipotent; not that He will always be. A possible rock which cannot be lifted doesn't nullify the fact that God was omnipotent in the moment at which we specified the axiom.
Now let us take the axiom "God was, is, and will always be omnipotent", a modification of Axiom B which we shall call Axiom C. Since God creating a rock which He is not able to lift would either reduce or nullify His omnipotence and we are considering Axiom C as fact; we can conclude that God never makes that choice although His omnipotence allows for the possibility. Remember that saying "will always be" is exclusively a prediction; not an observance.