Again, an entirely, massive topic in and of itself, but..... For our purposes here I would go with a simple operational definition. Something along the lines of: Reason describes a systematic methodology for the determination of knowledge given an incomplete environment. I can't recall saying such... (Though I will now...) While we have (and have had) many beliefs that have the appearance of contradicting rationality, typically, these beliefs are such simply due to a lack of investigation. Given sufficient analysis, such beliefs tend to disappear. However, there is a subset of such beliefs that, for ontological or epistemological reasons, may not lend themselves to investigation. I would say that 'god' is one such belief. As to handling this subset, it seems obvious to me that the members therefore must be deemed irrational. Note: this is not to make any judgment with respect to ontological status; I'm not saying "God does (can)not exist", but rather "It is not rational to behave such that God exists". I find that my position here is pretty much in accordance with most others'. Which is to say: the position of the religious (or, spiritual, etc.) person is one of faith, and (therefore) not one of reason. I have great respect and admiration for such people, though I do not understand them.