Both faith and reason are important: they are not per force antithetical, but might be deemed complementary. When faith is combined with reason, one has a faith that is neither blind nor credulous. As John Locke states:
"Whatever God hath revealed is certainly true: no doubt can be made of it. This is the proper object of faith: but whether it be a divine revelation or no, reason must judge; which can never permit the mind to reject a greater evidence to embrace what is less evident, nor allow it to entertain probability in opposition to knowledge and certainty" (An Essay Concerning Human Understanding, Book IV, Chapter XVIII.10).
He also insists: "Nothing that is contrary to, and inconsistent with, the clear and self-evident dictates of reason, has a right to be urged or assented to as a matter of faith" (Ibid.).
My observation on Locke's remarks: I would say that reason and the consistent witness of Scripture must determine whether a given datum constitutes divine revelation. We also need the Christian ecclesia to guide our thinking on divine revelation. However, like Locke, I would maintain that nothing which conflicts with "the clear and self-evident dictates of reason" should be considered or taught as a matter of faith.
Some reply that it's not always easy to determine what counts as a lucid and self-evident teaching that is rational, but the criterion for self-evidence in logic is fairly straightforward. Furthermore, it's not that hard to spot faulty reasoning or invalid and unsound arguments. But what some view as irrational may not be considered irrational by others. Yet logic does provide controls for what does or does not count as rationality. So we do not have to make subjective decisions about what teachings are rational or irrational since objective controls exist.