So Divine Middle Knowledge is God's knowledge of what each possible creature would do when placed in each possible situation. This allowed him to select which possible would to create in a manner that would best meet his goals for creation.
But can this view be backed up biblically? And where is the burden of proof?
The first point to note is that the Bible never talks about how God's foreknowledge works - it simply describes it. This means that proving it directly from biblical references is not really possible - but neither is proving any other view of divine foreknowledge either (nor indeed a large part of theology). Instead, there are a few passages that seem to directly imply middle knowledge, but the main argument is that it is the best explanation for a number of other passages combined together.
However, there are two main passages that show evidence of God's middle knowledge. The first is 1 Samuel 23:6-13:
This passage is interesting. It shows that God knew that if David were to stay at Keilah, Saul would come and try to destroy the town. And if Saul were to come to the town, the townsfolk would hand David over to him.
But this didn't happen - David left Keilah so Saul did not go there, and the townsfolk did not hand David over. This cannot be explained as God's simple foreknowledge, as they events did not happen. But God knew what would happen under different circumstances.
Matthew 11:20-24 says:
Here Jesus declares that if miracles had been performed in certain cities which did not repent, then they would have repented. Thus Jesus is claiming knowledge of what certain individuals would have done under certain different circumstances.
Both of these passages claim God's knowledge of what would have happened had the circumstances been different, and thus neither cannot be explained by simple foreknowledge (nor by open theism for that matter). God is claiming specific knowledge of potential circumstances that did not in fact occur.
It is a specific claim of God's middle knowledge.


Comments
I believe what the passages above refer to are God's conterfactual knowledge not middle knowledge. I think that Craig clarifies the differances between the two in his contribution in the Divine Foreknowledge: Four Views book. From what I understand it is divine counterfactual knowledge (knowledge of various events that could occur, despite what actually occurs), that provides a basis for the middle knowledge position, but other positions (namely the augustinian/ calvinistic position) affirm counterfactual knowledge and deny middle knowledge. Check out the fourviews book, especially Craig and Helm's contributions!! It will a be much greater help to you than I can be. Blessings!!