When I speak of reason or rationalism, all I mean is the conviction that we canlearn through criticism of our mistakes and errors, especially through criticism by others, and eventually also through self-criticism. The genuine rationalist does not think that he or anyone else is in possession of the truth; nor does he think that mere criticism as such helps us achieve new ideas. But he does think that, in the sphere of ideas, only critical discussion can help us sort the wheat from the chaff. He is well aware that acceptance or rejection of an idea is never a purely rational matter; but he thinks that only critical discussion can give us the maturity to see an idea from more and more sides and to make a correct judgement of it.
Reason is non-negotiable. Try to argue against it, or to exclude it from some realm of knowledge, and you've already lost the argument, because you're using reason to make your case. And no, this isn't having "faith" in reason (in the same way that some people have faith in miracles), because we don't "believe" in reason; we use reason.