Source : Webster's Revised Unabridged Dictionary (1913)

Arbitrariness \Ar"bi*tra*ri*ness\, n.
   The quality of being arbitrary; despoticalness; tyranny.
   --Bp. Hall.

Source : WordNet®

arbitrariness
     n : the trait of acting unpredictably and more from whim or
         caprice than from reason or judgment; "I despair at the
         flightiness and whimsicality of my memory" [syn: {flightiness},
          {whimsicality}, {whimsy}, {whimsey}, {capriciousness}]