The Collaborative International Dictionary of English v.0.48:

Unreasoning \Unreasoning\
   See reasoning.

WordNet (r) 3.0 (2006):

unreasoning
    adj 1: not based on reason or evidence; "blind hatred"; "blind
           faith"; "unreasoning panic" [syn: blind, unreasoning]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "unreasoning":
   arbitrary, blank, blankminded, brainless, calm, capricious,
   careless, emotionalistic, emotive, empty, empty-headed, fatuous,
   foolish, hammy, headless, heedless, histrionic, hysteric, ignorant,
   inadvertent, inane, incogitant, inconsiderate, inept, insensate,
   irrational, lackbrained, lean-minded, lean-witted, melodramatic,
   mindless, nirvanic, nonrational, not bright, oblivious,
   of little brain, overemotional, passive, pea-brained, pin-brained,
   quietistic, reasonless, relaxed, sensational, sensationalistic,
   senseless, slackminded, slackwitted, theatrical, thoughtfree,
   thoughtless, tranquil, uncalculating, ungifted, unguarded,
   unideaed, unintellectual, unintelligent, unoccupied, unreflecting,
   untalented, unthinking, unthoughtful, unwise, vacant, vacuous,
   witless