The existence of Paradise and Hell, the particulars of reward and punishment, and their relation to particular deeds cannot be exhaustively derived from observation or analogy.
Reason's function is to consider possibility, detect real contradictions, evaluate the messenger's evidence and correctly understand an established revelation. Revelation's function is to inform us about unseen matters that unaided reason does not disclose.
A detail's being unknown to reason does not make it impossible. The difference between not knowing that something exists and knowing that it does not exist is fundamental to these discussions.