I'm sure most of you remember the idiocy surrounding the Pope's speech at the University of Regensberg a little over a year ago -- protests, riots, violence, calls for beheading, burnings in effigy, etc. (which is so ironic that I actually hurt when learning of it).
Here's a snippet from the Wikipedia article on the topic:
The lecture on "faith and reason", with references ranging from ancient Jewish and Greek thinking to Protestant theology and modern Secularity, focused mainly on Christianity and what Pope Benedict called the tendency to "exclude the question of God" from reason. Islam features in a part of the lecture: the Pope quoted strong criticism of Islam, which he described as being of a "startling brusqueness, a brusqueness which leaves us astounded".
In three paragraphs at the beginning of the speech, Pope Benedict quoted from and discussed an argument made by the Byzantine Emperor Manuel II Palaiologos in a 1391 dialogue with an "educated Persian" (who remained unnamed in the Pope's lecture), as well as observations on this argument made by Theodore Khoury, the scholar whose edition of Manuel II's dialogues the Pontiff was referencing. Pope Benedict used Manuel II's argument in order to draw a distinction between the Christian view, as expressed by Manuel II, that "not acting reasonably is contrary to God's nature", and an Islamic view, as explained by Khoury, that God transcends concepts such as rationality, and his will, as Ibn Hazm stated, is not constrained by any principle, including rationality.
If you never had the opportunity or time to read it, here's an audio recording of the English translation: