Just because religions are mutually exclusive doesn't make them falsifiable - it just means you don't know which one is true.
Crash's distinction is a good one, but many religious viewpoints are not falsifiable even on points of fact. Noah's flood is thoroughly falsified in any number of ways, but if you're allowed to invoke miracles - supernatural interventions to circumvent natural law - then no scientific objection matters. Indeed, many creationist organizations explicitly state than on any matters that science conflicts with the revealed word of God, science must be mistaken, and will eventually be shown to be consistent with scripture.
That's pretty frickin' unfalsifiable.
Edited by Zhimbo, : typo fix.
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