The Collaborative International Dictionary of English v.0.48:

Selfness \Self"ness\, n.
   Selfishness. [Obs.] --Sir. P. Sidney.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "selfness":
   agreement, coequality, coincidence, congruence, correspondence,
   differentiation, differentness, distinctiveness, egohood, equality,
   equivalence, homogeneity, homoousia, human factor, identity,
   indistinguishability, individualism, individuality, integrity,
   no difference, nominalism, nonconformity, oneness, particularism,
   particularity, personal equation, personal identity, personality,
   personship, sameness, self-identity, selfhood, selfsameness,
   singularity, soul, synonymity, synonymousness, synonymy,
   uniqueness, unity