Pope Benedict XVI delivered a lecture at the University of Regensburg in Bavaria, in his 2006 speech, simply titled Faith, Reason and the University: Memories and Reflections, Benedict characteristically took up a knotty concept the interplay of faith and reason. He wanted to show how reason untethered from faith leads to fanaticism and violence.
To illustrate that case, Benedict dug up a 14th-century dialogue between a long-forgotten Byzantine Christian emperor, Manuel II Paleologus, and a Persian scholar about the concept of violence in Islam.
Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached, Benedict quoted the emperor as saying to his Islamic interlocutor.
In Islamic teaching, Benedict said, God is absolutely transcendent. His will is not bound up with any of our categories, even that of rationality.