In science everything must add up, form equations, be tested, proven and correct.
In imagination, on the other hand, the Sun can be composed of cheese. Any idea, however ridiculous can be obsessed over and violently defended.
We must be careful not to believe things simply because we want them to be true. No one can fool one as easily as one can fool oneself 
Why should one believe in anything? The way is observation and examination, and not belief.