Here's a pretty interesting talk about the birth of the Mu'tazilite, or rationalist, sect of Islam and their opponents, the Ash'arites, who are now largely the mainstream. He talks about how the ancient Greek philosophy was incorporated into Islamic thought by one of the Caliphs, and how this was later opposed by other theologians.
Essentially, there were Muslims who adopted and embraced reason, and those who eschewed it, and Islam has subsequently suffered from this rejection.
http://www.youtube.com/watch?v=bhB1T9Q901s&feature=channel_video_title