Irrational Dichotomy (n): Division into two mutually exclusive, opposed, or contradictory groups: a dichotomy between thought and action, or holding two contradictory beliefs simultaneously.
When a person is exposed to evidence which runs counter to their previously held notions of reality, there exists within their mind a contradictory dichotomy of ideas which must eventually become resolved. This is an uncomfortable, and often distressing time for them and can, if un-resolved for an extended period of time, lead to mental illness.
Christians, and indeed all Religious adherents, fall into this group. And they are not allowed to resolve these dichotomies.
Understanding and enlightenment comes to one when that dichotomy is ultimately resolved and beliefs once again fall in-line with observable reality.