The Collaborative International Dictionary of English v.0.48:

Alterity \Al*ter"i*ty\, n. [F. alt['e]rit['e].]
   The state or quality of being other; a being otherwise. [R.]
   [1913 Webster]

         For outness is but the feeling of otherness (alterity)
         rendered intuitive, or alterity visually represented.
                                                  --Coleridge.
   [1913 Webster]