If you go over to Triablogue, you will find all sorts of dismal remarks about how poorly I have made the case for the critics of Calvinism. In the process I do think I have learned a good deal about who Calvinists think about the relevant issues. With respect to some issues, related to biblical interpretation, I don't think I have anything to add to the discussion that has not already been brought up in other discussions of the subject.
What maybe I have come up with, however, is an argument concerning the concept of glory that I don't think has been satisfactorily answered.
To do this I need to narrow my claims a little bit. Initially, when I blogged on this 3 years ago, I said that Calvinists can't solve the problem of evil. But, very quickly, I had to acknowledge that "solving" the problem of evil is a tall order and that it may be difficult to anyone to solve it.
Most study of the problem of evil suggests that with respect to a portion of human suffering, we can come up with possible scenarios according to which we can see why God would permit it. With other suffering, we aren't in a position to see why it occurs, but we are nevertheless entitle to believe that there is an answer even if we can't see it.
With respect to some evils, it seems possible and in some cases easy to see why God permits them. With others, there is considerably more mystery.
Let's take the evil of everlasting suffering in hell. On a free will view I can see how someone might end up permanently in rebellion against God and unable (because they are unwilling to serve) to receive the joys of heaven. Read The Great Divorce for how that goes. But why, on a Calvinist view would anyone end up in hell?
The first answer for the Calvinists has to be that they are sinners and deserve it. This assumes a couple of things, first that a temporal sin can deserve an infinite amount and duration of punishment, and second that humans can deserve retributive punishment for actions that they are determined by another to perform. (This is a strong form of compatibilism. Many compatibilists are not retributivists about punishment. They argue, for instance, that even if determinism is true, you can still deter crime by punishing criminals.) But let's grant these highly counterintuitive claims for the sake of argument. We still need to explain why God would create a permanently unrepentant sinner, when he could preordain them not to sin or preordain them to receive God's irresistible grace and save them.
The unanimous answer in Calvinist theology seems to be that God does it for his own glory. This seems as little counterintuitive as well--people who cause others to suffer for their own glory here on earth are considered bad, not good. But let's grant that counterintuitive claim also. Glory, it seems to me, analytically requires that it be glory in the eyes of someone. (Is there any Scripture verse that suggests a different conception of glory?) On the face of things, the way a God pursuing his own glory to achieve that goal would be to save everyone so that there could be as many people as possible praising Him forever. But no, Calvinists say that God can demonstrate his wrath against sin by having some lost people (lots and lots of lost people, actually). The idea, I take it, is that the saved will praise God more because they recognize God's holiness and absolute opposition to sin by seeing people in hell. And my response is that God, as an omnipotent and completely sovereign being can decree into place any state of mind that he wants without having to use the means of damned souls to create this glory for himself. (Let's also put to the side any Kantian worries about using people as a mere means). So the instantiation of damned essences doesn't serve any conceivable greater good, because that good could be accomplished without the damnations.
I read the Walls passage that Paul referenced about God's glory in damnations, according to which people in heaven see that God has done everything possible to save someone but respects their freedom. Even there I don't think Walls holds that the ultimate purpose of all God's actions is to glorify himself.
Now, the Calvinist can respond by saying that there is a purpose for reprobations, even though we have no clue as to what it is. In fact, Paul constantly reminds me that I said that there have to be possibilities for God that we are not in a position to consider. However, unlike Paul, I am kind of agnostic about what will transpire eschatologically, or how it works. Calvinists claim that they know that there will be some people in hell and that God's predestination, through the means of their own sin, puts them there. The agnosticism the Calvinist at this point can insist upon concerns why.
My conclusion is if people are reprobated there is no understandable reason why this is so. It is completely and totally beyond my comprehension. I can't even see through a glass darkly how this could possibly be justified. The reasons that are offered for reprobating people don't work even on their own terms. That doesn't make the position impossible to hold, just, at least to my mind, a whole lot more difficult. Everyone uses mystery maneuvers at some point (even materialists!) but the less you use them, the more epistemically adequate your position.
What I have shown here is that Calvinists cannot solve the problem of the evil of eternal suffering in hell, in the sense that they can't provide any understandable reason for it. This is a narrower claim than what I began with, but it is still not completely without significance for the credibility of Calvinism.
I'm not appealing to intuition here. Calvinism is counterintuitive in many ways, but I am simply arguing that whatever glory God wants or needs he can accomplish without inflicting eternal punishment on anyone. Therefore, even granting several Calvinistic assumptions, eternal damnation remains an apparently gratuitous evil.
Arminians can "solve" the problem of reprobation in the sense that considerations from their own theology make it somewhat understandable, though hardly problem-free.
It's my contention, however, that the more you appeal to mystery, the worse it is for you epistemically. The more of an explanation you can have for suffering, the better your theology is, all things being equal.