A world containing creatures who are significantly free (and freely perform more good than evil actions) is more valuable, all else being equal, than a world containing no free creatures at all. Now God can create free creatures, but He can’t cause or determine them to do only what is right. For if He does so, then they aren’t significantly free after all; they do not do what is right freely. To create creatures capable of moral good, therefore, He must create creatures capable of moral evil; and He can’t give these creatures the freedom to perform evil and at the same time prevent them from doing so. As it turned out, sadly enough, some of the free creatures God created went wrong in the exercise of their freedom; this is the source of moral evil. The fact that free creatures sometimes go wrong, however, counts neither against God’s omnipotence nor against His goodness; for He could have forestalled the occurrence of moral evil only by removing the possibility of moral good.
Plantinga’s argument is that even though God is omnipotent, it is possible that it was not in his power to create a world containing moral good but no moral evil; therefore, there is no logical inconsistency involved when God, although wholly good, creates a world of free creatures who chose to do evil.
I think the defense is flawed. First, it starts with a value judgment which is subjective, and which I can’t agree with either. Why is an non-free world without evil less valuable than a free world with evil? I wouldn’t hesitate to choose for the non-free world without evil, I’d be happy with the illusion of having a free will. For all we know we could be living in a world with such an illusion of free will right now. Of course it is much more valuable if people would decide to do good out of free will instead of a non-free will, but that’s just one aspect of the value of free will which pales in importance when compared to the value of the absence of evil.
I agree that God couldn’t cause free creatures to do good because that would cancel out their free will. But, as is also clarified in the second quote, Plantinga thinks that ‘even though God is omnipotent, it is possible that it was not in his power (etcetera)’. Another flaw, because being omnipotent means that nothing is impossible. Of course it all depends on how omnipotence is defined, and I’m merely giving my interpretation of omnipotence here. In the end it all comes down to that and all the logic to construct the defense is useless.
Apparently I’m discussing the omnipotence paradox, which is also covered by Wikipedia, so unfortunately I’m not thinking of something new. After reading all of it I think it present some clever solutions, such as that omnipotent beings cannot do the logically impossible while still retaining their omnipotence. But that’s only true if you assume the being is not accidentally omnipotent. The solution presented by Descartes is totally lame because it says omnipotent beings aren’t constrained by logic. If omnipotent beings are placed outside logic, you can’t describe them with logic either and they become meaningless.
All thought about omnipotence is pointless anyway, because it was probably invented by people who did not consider the logical problems of the concept. Only gods are considered to be omnipotent and they haven’t been proven to exist through the use of the scientific method.