At what point does faith become insanity?

[Angrboda]

Two things. Mental illness is generally reserved for describing mental processes over which the individual has little or no control. I don't think that fairly characterizes religious belief. The second is that this ignores our innate capacity for compartmentalization. So we can believe both things that are irrational and things that are rational at the same time without any harm to the person. Thus a person can believe they are going to heaven when they die, yet not act on that belief when deciding whether to cross in front of traffic or not. The idea that religion and the mind are one unified thing in the mind leads to erroneous conclusions about it.