In the end, people believe whatever they want. Facts, reason, and logic make little difference. Faith will trump the truth every time.
"The Critique of Pure reason" by Emmanuel Kant.
Thus it makes sober sense to say, "I believe in order to understand." "I believe that without which nothing else is believable."
The question for the Muslims --- a serious question ---is whether they "believe" that faith must be reasonable -- must follow some interior set of laws which may transcend, but may not contradict, the truths apprehended by reason.
As we saw from Benedict 16's Regensberg address, it's a question which many Muslims find almost intolerably disturbing.