The Collaborative International Dictionary of English v.0.48:

Disinterestedness \Dis*in"ter*est*ed*ness\, n.
   The state or quality of being disinterested; impartiality.
   [1913 Webster]

         That perfect disinterestedness and self-devotion of
         which man seems to be incapable, but which is sometimes
         found in woman.                          --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

disinterestedness
    n 1: freedom from bias or from selfish motives