The Collaborative International Dictionary of English v.0.48:

demythologization \demythologization\ n.
   the restatement of a message (as a religious one) in rational
   terms.

   Syn: demythologisation.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

demythologization
    n 1: the restatement of a message (as a religious one) in
         rational terms [syn: demythologization,
         demythologisation]