As if the behavior of Joseph wasn't bizarre enough, he now pretends that Benjamin has stolen Joseph's divining cup. Why? Why not hide gold or jewelry in Benjamin's sack?
We don't know the answer. Joseph was a prophet (He could interpret dreams) and Hebrews 1:1 tells us that in ancient times, God spoke to the prophets in many different ways. Joseph MIGHT have been telling the truth about being able to divine with the cup.
The symbolism is that God gives the Church (pictured by Benjamin) the ability to know His will. Hostile to their brother, not fearing the Lord, and lacking both knowledge and wisdom, the other ten brothers couldn't discern God's will, but Benjamin could.
Strengthening the Church is a successful means of resolving conflicts among the people of God.