This is Gale's critique of Adams' response to the problem of evil.
With this concept of middle knowledge in mind, a dilemma argument can be constructed to show that that God cannot bestow salvific grace in advance.
Either God has middle knowledge or he does not.
If God does not have middle knowledge, then God cannot grant salvific grace in advance. first horn
If God does have middle knowledge, then God cannot bestow salvific grace in advance. second horn
God cannot bestow salvific grace in advance. From 1-3
On either horn, Adams's theodicy of grace does not work. Each horn will now be argued for separately.
Argument for the First Horn
In "Middle Knowledge and the Problem of Evil," Adams argued at length that it is impossible that God create free persons and also have middle knowledge of what they will freely do. Thus, Adams is personally committed to attacking the first horn of the dilemma argument. This, of course, is only of ad hominem interest since it concerns internal consistency within Adams's philosophy. Unfortunately, it looks very much like God must have middle knowledge in order to be able to bestow salvific grace in advance upon the free people he creates. For God cannot bestow salvific grace in advance unless he knows at the time of his creative act that he is doing so. But he cannot know that he is doing so unless he knows that the free persons he creates will prove themselves morally unmeritorius by their subsequent free actions. This requires that God have middle knowledge prior to his act of actualizing a possible free person, that is, he must know that if he were to actualize this possible free person's diminished possible free person, the instantiator would freely perform at least one morally wrong action. In other words, he must know the relevant F-conditionals predicting how the instantiator of this diminished possible free person would freely act if it were to be created. Without the requisite middle knowledge, God's creation of free persons is a gamble, since he cannot have any prior assurance that these persons will come through for him and freely do the morally right thing. This makes availble (sic) to God the morally exonerating excuse for permitting moral evil of unavoidable ignorance. But whatever merit this might have in providing a theodicy for God's permitting moral evil, it precludes his granting salvific grace in his very act of creating free persons.
VR: But since Adams is a card-carrying universalist, it looks like he can dodge this objection. Everyone gets saving grace.