Alvin Plantinga is considered by most philosophers to have reinvigorated the philosophy of religion with his insights on the problem of evil, the nature of necessity, and warrant and basic belief. In other posts I've considered how his free will solution relies on a definition of freedom that requires uncaused events. Here I'd like to consider his beliefs about what it means for God to have created a good world. This can be found in his essay titled "Supralapsarianism."
His view is that God is a necessary being who exists in all possible worlds and consequently all worlds contain the good of God's existence. Plantinga is a Molinist which means he analyzes God's act of creation in terms of God considering possible worlds and actualizing the one which accords to his good will. This is a world that contains the goods of free choice (which leads to the fall) and salvation through Christ's atonement.
This solution is consistent with Plantinga's response to philosophers like J.L. Mackie who say that the problem of evil is a logical problem which proves that God does not exist. By way of contrast, Plantinga argues that it is not a logical problem because there is a good reason for God to permit evil. The essential detail that will make or break this answer is exactly what that good turns out to be.
For Plantinga, it is the atoning work of Christ and the salvation it provides. He argues that Christ demonstrates the love of God in a way that nothing else does.
My concern is that salvation as the good doesn't seem to tell us what the good actually is. To be saved is to be saved from evil so that one can be good, meaning salvation itself isn't the good. If the good is the love of God then its not clear why this necessitated Christ's death. If salvation requires Christ's death as the atoning payment then we're still left wondering to what good humanity is restored through this salvation.
We are a little closer when Plantinga speaks about what the work of Christ reveals about God. However, to locate this in Christ, rather than Christ's atonement restoring to the good, confuses the order between these. And perhaps this is what the infralapsarians were getting at, and certainly how Charles Hodge defends them. There is a logical order between creation, fall, and redemption, as well as a temporal order.
Plantinga seems to slip into this mistake for a common reason: making salvation the good. Because salvation is the focal point, God's purpose in history is reduced to salvation. However, if the good becomes the focal point, and salvation is a means to the good, we restore the order between creation, fall, and redemption. This allows us to consider the chief end for which God created man, how the fall distorted that chief end, and how redemption restores man to the good.
Before we can appeal to the atonement as the crux of a solution we must ask if this idea is meaningful. I argue that it is not meaningful to speak about the need for atonement apart from speaking about what is inexcusable and requiring of atonement. Specifically, if it is not clear that God exists then unbelief is excusable, as are all the fruits that grow out of unbelief, and therefore humans in unbelief do not need atonement. Consequently, any appeal to the death of Christ must be built on the clarity of general revelation to be meaningful. When this clarity is not present, the result is that the death of Christ is reinterpreted as not atoning work but rather an example of love, or a virtuous act. The need for atonement is abandoned.
I discuss this further in my chapter about Plantinga and Reformed Epistemology which appears in my book "Reason and Worldviews."