Over at Skeptic Blogs, there is a rather long but reasonably thorough look at an attempt to make the term “faith” not antithetical to reason. I just want to give a bit of historical background to the first millennium of Christian understanding of reason and faith.
Scholars that have studied the interaction of science and religion often take an look at the first centuries of Christendom (in periods often called Late Antiquity and the Early Middle Ages), and David Lindberg is probably the best known and most respected on the subject. What he concluded is basically the thesis of Augustine, that science/philosophy/reason are the handmaiden of religion/theology. Reason can be used to help in theology, but it cannot be used to undermine it. (See his essay in God and Nature.) That seems to have been the position of Christians from earliest times to the Middle Ages and beyond as well.
And that is inherently non-rational: to say that you cannot use reason to see if a major aspect of research or understanding of the world has the gravitas it deserves is obviously not the way to go and be called rational. And that is what the faith part means: trust this source, and do not question it.
Now, it is possible to do science under this sort of constraint (so long as it doesn’t contradict the faith at any point), but it also doesn’t encourage it. And that is part of why the Scientific Revolution came rather late, even though the Greeks and Romans were doing science. This sort of problem is well-illustrated in Richard Carrier’s chapter on ancient science in The Christian Delusion, as well as proving that Christianity was not responsible for modern science as some have argued.
Perhaps it is no wonder then that the early Christians didn’t provide reasons for their faith, but did more to insult opponents and beg disciples to believe in things unseen and evidence hoped for (Hebrews 11:1). And that sort of strategy can get you hurt.