Solo said:
Can God create a rock too big for himself to pick up?
Yes.
And then he could pick it up.
More seriously, you're asking about a logical paradox. Can God do both A and !A? He could not both send Jesus to die for our sins and not send Jesus to die for our sins. He could not both create Adam and Eve and not create Adam and Eve. At least, not in the sense that we understand such concepts. Perhaps he
could transcend such logical pitfalls in ways that we can't fathom, because he is, after all, omnipotent. But it's not a diminuation of his power to presume he can't do that which would violate notions of causality.
It is, however, a diminuation of his power to presume that he can't do something just because we have decided that thing is against his character. Now, perhaps you're operating under a post hoc definition of "could", such that if an eternity transpires and X has not happened, then X
can't happen. But I think such definitions, while useful in describing mortal issues of calculus and probability, fail when they concern the will of an omnipotent deity.
Could God have decided not to send down Jesus? Sure, he could've, because he's omnipotent. But he didn't, because he loves us. Could God have decided to say to hell with the lot of us and wipe the universe clean in a cataclysm of divine wrath? Sure, he could've, because he's omnipotent. But he didn't, because he is omnibenevolent. Could God decide that being good is a pain, and he'd like to get drunk and frolick with women of loose virtue? Well, yeah, because he can do whatever he pleases. But he never would in all of eternity, because he chooses not to do things that are sinful.
In claiming that God is fundamentally incapable of doing certain things, you've reduce him to a mindless automaton, bound by fate and constricted by cosmic forces beyond his control. A God who can do sinful things but elects not to because they are, in fact,
sinful is a much greater, more majestic, and altogether more admirable being. As God is the greatest of all possible beings, it stands to reason that this must be the case.
You may disagree. That's fine. But realize that it's not because you love God more, or you're more mature, or you've been given the keys to the celestial washroom because God likes you more. Reasonable people, equally mature in their relationship with God, can disagree about the finer points of Godhood. See, this is because
none of us are God, and thus none of us know for sure. When we die, we can go ask him, and whoever's wrong can buy the other guy a heavenly drink. (Henry Weinhardt root beer, of course, because in heaven this sweet ambrosia is all that exists.) In the meantime, we should be respectful of differences of opinion regarding such minor trivia as why,
precisely, God doesn't sin.