Even if there is not a best of all logically possible worlds, I think the Molinist will want to insist that there is either a best of all logically feasible worlds (in light of which counterfactuals obtain) or a class of ‘best of all logically feasible worlds’. Let’s say that two worlds w1 and w2 are equally good, and both are logically feasible. w1 and w2 are nearly identical worlds, but w1 is a world in which “Tommy is saved and Susie is lost” whereas w2 is a world in which “Tommy is lost and Susie is saved.” If other things ‘must’ change given which of these conjunctive facts is true then we can simply stipulate ‘mutatis mutandis‘ and say that even given such changes the worlds are equally good. If w1 and w2 are both equally good worlds, and if there is not at least one other logically feasible world which is better, then God will choose to actualize either w1 or w2. However, what sufficient reason can God have for choosing either one over the other? None, obviously, given that I’ve already stipulated that neither one of these worlds is in any respect ‘better’ than the other. The Molinist already rejects the PSR though, so it won’t be a problem for her to say that God actualizes one of these worlds without any sufficient reason. So, God will have to arbitrarily choose to actualize one of these worlds, and fail to actualize the other.
Let us suppose that God arbitrarily chooses to actualize w1. Now the Molinist says that nobody is lost or saved because of the accidents of history, geography, genetics, psychology or the likes of such. However, here, clearly Susie is lost and Tommy is saved by the accident of God’s free choice to actualize w1 instead of w2. Perhaps Susie is in some sense still responsible, given that, in w1, she is lost as a consequence of libertarian free choices (or one great big Libertarian free choice), but Susie is still lost by reason of an accident, something entirely out of her control. How is the Susie of w2 any better off than the ‘Susie’ who is freely lost by reason of a historical or psychological accident beyond her control? Such accidents do not negate free will anymore in one case than they do in the other. So the Molinist, it seems to me, reintroduces the problem with one hand that she promised to take away with the other.
Perhaps the Molinist could argue that God would actualize all and only the best of all logically feasible worlds (so that God might actualize, in this case, w1 and w2). This is like a very moderate appeal to what I earlier called a theodicy of extreme modal realism (maybe extreme ‘feasible’ realism or something). I don’t think it will help much, however, for the problem of accidental salvation remains – in w1 Susie is accidentally lost, and in w2 Tommy is accidentally lost. Salvation becomes irreducibly accidental on the Molinist account.
I think this gives us more reason to prefer a Thomistic/Augustinian solution, rather than a Molinist solution. By ‘Thomistic/Augustinian’ solution I have in mind something like that God provides at least a sufficient super-abundance of Grace to all men according to the accidental circumstances they find themselves in – sufficient, that is, for their salvation. That is a much more elegant, tidy, aesthetically pleasing, and unproblematic solution.