Looter, I think we are coming from different places when discussing rationality and irrationality.
I am approaching irrationality as the brain's emotional response as opposed to a logical response. I think of it in terms of rightbrain/leftbrain functioning.
Belief springs from the brain's desire to fulfill its emotional needs (right brain). Logic springs from the left brain's need to be organized and rational - it is concerned with the detail of the material world - the right brain likes a big picture way of perceiving the world. The right brain speaks through emotion - the left brain speaks through the rationality of language.
Belief satisfies our emotional need to stay connected to the material world