Many theists are libertarians about free will. I take it as a minimal implication of libertarianism that at any time t at which an agent S freely chooses A, S might have chosen ~A instead. The future branches into many genuinely possible alternatives. I want to make a few observations.
1. Note first that the free will defense (FWD), as Plantinga offers the argument, simply assumes that we have libertarian freedom. It is the assumption of libertarian freedom that makes it possible for (what I’ll call) bad CCF’s to be possibly true: recall we are invited to consider a world in which CCF’s of the sort, God creates S in T ☐⟶ S goes wrong, are true. Such counterfactuals could not be true unless we assumed that there are worlds in which God exists and agents produce evil. He could have ended the argument right there, after affirming that at least one of these is true somewhere in metaphysical space, since that is the conclusion we’re after.
2. That brings me to my second quick observation. For all of the fuss in the FWD, all we really need, for Plantinga’s purposes, is one counterfactual of the sort, God creates S in T ☐⟶ S goes wrong, to be true in some possible world. The rest of the argument is unnecessary for the main purpose. If there is such a true counterfactual, then God exists in some world where there is evil, contrary to the logical argument from evil. So ends the dispute.
My main point is that atheological opponents might reasonably balk at the idea that libertarian freedom is compatible with theism. Here’s why. Assume we have libertarian freedom. For any rational agent S, if S has libertarian freedom with respect to action A, then S can perform ~A. For actions A with moral significance, libertarian freedom entails that you can perform the morally wrong action ~A. But the modal claim that you can perform the wrong action ~A entails the further modal claim that God can actualize a world in which you go wrong. So far, I assume, so good. Now, unless it is true that you and everyone else is universally transworld depraved in every possible world in which you go wrong, which is simply not credible, this means that God can actualize a world in which you go wrong when he might have actualized a world in which you go right instead. Certainly, there is some world like that under the assumption of libertarianism. But why should an atheological opponent accept that? He shouldn’t. Why wouldn’t an atheological opponent urge instead that God cannot actualize a world in which you freely go wrong when he might have actualized one in which you freely go right. He would. But then it’s reasonable to believe that libertarianism is not compatible with theism.