Does open theism have any advantages vis-a-vis other theories of divine providence, in particular, theological determinism (hereafter 'Calvinism') and theological compatibilism (hereafter 'Molinism'), with respect to the problem of evil? The answer, I think, is a clear 'Yes'. Before stating my case, let me briefly define my terms.
By Calvinism I mean the view that God has, as the Westminster Confession of Faith puts it, meticulously decreed "whatsoever comes to pass". In other words, everthing that happens ultimately does so because God sovereignly willed it to happen, and there are no limits, other than those coming from God's own nature, that contrain what God can bring to pass.
By Molinism I mean the view that God has meticulously decreed whatsoever comes to pass, but that there are limits
apart from God's own nature, that constrain what God can bring to pass. Specifically, according to Molinism, God's creative decision is based on his pre-volitional knowledge of so-called (would-) counterfactuals of creaturely freedom (CCF's), over which he has no control. Thus, according to Molinism, God knew, for any possible free creature S placed in any possible free choice-situation C (with circumstance-relative options A and not-A), either that
If placed in C, S would freely do A or that
If placed in C, S would freely refrain from doing A (i.e., do not-A). Because God has no control over which of these counterfactuals are true, his creative options are narrowed from the class of all
possible world to the class of all
feasible worlds (i.e., those possible worlds that are compatible with the true CCF's).
By open theism I mean the view that God has
not meticulously decreed whatsoever comes to pass but rather has left some aspects of history 'open', to be determined by the free decisions of his creatures.
Finally, the problem of evil is a standard challenge to theism to reconcile the existence of an all-good, all-powerful God with the existence of extensive, and often apparently gratuitous, evil in the world. Theists generally try to meet the problem, at least in part, by developing 'theodicies' that try to explain how God is justified in allowing various kinds of evils in the interests of promoting various kinds of goods. There are many theodicies that have been proposed, but it is generally agreed that the most useful and plausible theodicies center around what is known as the Free-Will Defense. The basic idea is that giving creatures free will, so that they can genuinely choose between good and evil, is a really good thing because it makes possible things like genuine loving relationships that would not be possible otherwise. But, so the idea goes, God
could not have given creatures free will and also have guaranteed in advance that they never misused it. Thus, God is justified in giving us free will (because it is such a good thing), but when creatures do misuse it to do evil, it is they, and not God, who are to blame.
Of course, the Free-Will Defense is not a complete theodicy on its own. In particular, it says nothing about the suffering resulting from 'non-moral' evils like earthquakes and tsunamis. But it does seem to go a decent ways toward reconciling 'moral' evil with theism.
Now, let's look at our three theories of divine providence.
Calvinism as I've defined it seems clearly more limited in its theodical options because it has to eschew the Free-Will Defense. After all, if theistic determinism is true, then God can be 100% assured of getting exactly what he wants. Hence, if such a God exists, then it follows that God does get exactly what he wants. If the Holocaust happened, then God must have specifically wanted it to happen. Why? God only knows.
Furthermore, Calvinism implies that God has created either the best of all
possible worlds, or, if there is more than one such world, then one of the class of best possible worlds, or if there is no precise standard for determining a class of "best" possible worlds, then one of the class of "pretty darn good" possible worlds. It is far from clear, however, that this is such a world.
Molinism seems to fare better. The counterfactuals of creaturely freedom (CCF's) that it posits possess their truth values independently of God. Thus, if God creates Adam and puts him in a certain situation, then God can be certain ahead of time that Adam will freely choose to sin, and God can do nothing about it short of either not creating Adam or creating him but not allowing him into any situation in which he would freely choose to sin. So God can't be sure of getting anything he might want because the truth values of CCF's limit his options.
In addition, the Molinist can make some use of the Free-Will Defense, for if Adam freely sins, then God is at least partially exonerated because Adam is the one who sinned, and nothing God could have done could have prevented Adam from freely sinning in the very conditions in which he does freely sin.
But, one wonders, why
didn't God do something different if he was sure that Adam would freely sin? One suggestion is that Adam, along with every other free creature God could have created, possessed "trans-world depravity". In other words, no matter which free creature God could have created, eventually that being would have chosen to sin if allowed into any significant range of circumstances. I must admit that I find this idea of trans-world depravity highly implausible. Surely, one would think, given the trillions upon trillions of possible free creatures that God could have created and the unknown multitudes of circumstances he could have situated them in, surely
at least a few of them wouldn't have done what Adam did. And if so, then why didn't God create that kind of world instead?
Furthermore, Molinism implies that God has created either the best of all
feasible worlds, or, if there is more than one such world, then one of the class of best feasible worlds, or if there is no precise standard for determining a class of "best" feasible worlds, then one of the class of "pretty darn good" feasible worlds. Again, it is far from clear that this is such a world.
What about open theism? Open theism rejects the meticulous providence of both Calvinism and Molinism. So we don't have the problem of God eternally decreeing evils or of God's willing to create a world that he definitely knew ahead of time would contain all the evils that ours does. According to open theism, God has sovereignly decided to create a world with libertarianly free creatures and, since there are no true (would-) counterfactuals of creaturely freedom for God to know and since, according to open theists, libertarian freedom is incompatible with meticulous foreknowledge, God
could not know for sure ahead of time what kinds of choices his free creatures will make. God would seem to be less blameworthy for not preventing evils that he didn't know in advance would happen.
On the open theist view, an all-good God would be expected to create not the best of all possible worlds or the best of all feasible worlds, but the best of all possible
means to the best of all possible worlds. Or if there is no unique best means, then one of the class of best possible means. Or, if there is no precise standard for determining a class of "best" possible means, then one of the class of "pretty darn good" possible means. Or, qualifying the goal as well, a "pretty darn good" means to a "pretty darn good" possible world. And now, I think, it is not so clear that our world is not such a world. Not knowing in advance what choices his free creatures would make, the God of open theism would have to govern in accordance with
general policies to maintain a high probability of things staying on track.
But surely God knew in advance that it was
possible for egregious evils to happen? Why, then, didn't God "head them off at the pass", so to speak? One possibility is this: If God curtails our freedom to do egregious evil, then this would also curtail our freedom to do extraordinary goods. Perhaps any general policies that could have ensured that there be no Holocaust would also have ensured that there be no individuals like Mother Theresa.
Okay, but could the God of open theism be guaranteed to defeat evil in the end? In short, Yes. Despite what some critics have charged, God never surrenders his sovereignty in the open theist model. The world remains exactly as open as God wants it to be, no more and no less. Thus, if God wants to put an end to evil once and for all, all he has to do is call "time up" and judge the world. If he has decided to put up with evil for the time being, that is presumably because he thinks that the chances are high that much of it can still be turned for good.
In summary, then, I conclude that open theism does fare significantly better vis-a-vis its two main competitors with respect to the problem of evil. Of course, this is not to say that the problem of evil is not a serious problem for the open theist, just that the problem is somewhat more tractable.