There are numerous responses to the problem of evil, but first I want to point out an obvious logical problem that anyone who would question the libertarian runs into, and that is the Grandfather paradox. Since the libertarian believes that God foreknows actual future acts, then if God foreknows what a free creature will do in the future, he cannot not create that person, otherwise His foreknowledge of what the person will do would be wrong (since the person would not in fact do what God knew he would do; indeed, God's foreknowledge of the person's existence would be wrong as well!), and God cannot be wrong. If you want to introduce middle knowledge (or whatever you may call God's hypothetical knowledge) then I would just point out, as a friend has done, that "God can only have middle knowledge...of people who will certainly exist at some point. He cannot know what someone who never exists would do; there is no person there to ever know anything about."
There are several problems with this argument:
1. Brennon’s argument assumes that God’s foreknowledge of human actions is the effect of human actions. But since a Christian compatibilist wouldn’t take that for granted, this is only a logical problem given libertarian assumptions which the compatibilist doesn’t concede in the first place. Since I don’t think God’s knowledge of future human actions is causally contingent on future human actions, Brennon’s analogy with the Grandfather paradox is a nonstarter.
2. An ironic consequence of Brennon’s backwards reasoning is that all of God’s creative, miraculous, and providential actions are frozen. God’s knowledge of the future is contingent on the autonomous eventuation of the future such that God’s actions in relation to the future are utterly constrained by the future outcome. God’s field of action is dependent on independent factors. Man is free, but God is necessitated. For the future is inevitable–based on what we will do, rather than God’s doing. And not just human actions–but any future entity.
3. Brennon also makes the eccentric claim that God can’t know what someone would do unless God knows what someone will do, in which case the agent must exist at some point.
But hypothetical knowledge isn’t knowledge of what someone will do, as if there is only one possible course of action. In the nature of the case, hypothetical knowledge involves the knowledge of alternate scenarios.
4. There is also the specter of circular causality in supposing that God’s creative fiat is conditioned by our actual existence at some point down the line.
5. Brennon treats it as self-evident that God can’t know what we will do or would do unless we exist at some point down the line. But that’s a poor argument for libertarian theism:
i) God could know what we would do if what we would do is the reflection of God’s infinite imagination–like a novelist who can mentally entertain alternate endings to his own story.
ii) God could know what we will do if what we will do is the result of God planning our lives and putting his plan into effect.
Brennon reduces God to a cosmic waitress whose creative contribution consists of adding hot water to freeze-dried humans.