The Collaborative International Dictionary of English v.0.48:

Sureness \Sure"ness\, n.
   The state of being sure; certainty.
   [1913 Webster]

         For more sureness he repeats it.         --Woodward.
   [1913 Webster]

         The law holds with equal sureness for all right action.
                                                  --Emerson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sureness
    n 1: freedom from doubt; belief in yourself and your abilities;
         "his assurance in his superiority did not make him
         popular"; "after that failure he lost his confidence"; "she
         spoke with authority" [syn: assurance, self-assurance,
         confidence, self-confidence, authority, sureness]
    2: the quality of being steady and unfailing; "sureness of hand"

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "sureness":
   absolute certainty, absoluteness, acceptation, acception,
   acquiescence, act of God, arrogance, assurance, assuredness,
   belief, certain knowledge, certainness, certainty, certitude,
   cocksureness, confidence, confidentness, conviction, courage,
   credence, credit, credulity, dead certainty, definiteness,
   dependability, dependence, determinacy, determinateness, faith,
   faithworthiness, fate, fatefulness, force majeure, hope, hubris,
   incorruptibility, indefeasibility, ineluctability, inerrability,
   inerrancy, inescapableness, inevasibleness, inevitability,
   inevitable accident, inevitableness, inexorability, infallibilism,
   infallibility, inflexibility, inviolability, irrevocability,
   necessity, nonambiguity, noncontingency, overconfidence,
   oversureness, overweening, overweeningness, poise, pomposity,
   positiveness, predestination, predetermination, pride, probatum,
   proved fact, reception, relentlessness, reliability, reliance,
   reliance on, responsibility, security, self-assurance,
   self-confidence, self-importance, self-reliance, settled belief,
   stock, store, subjective certainty, surety,
   suspension of disbelief, trust, trustability, trustiness,
   trustworthiness, truth, unambiguity, unavoidable casualty,
   unavoidableness, uncontrollability, undeflectability,
   unequivocalness, unfalseness, univocity, unmistakableness,
   unperfidiousness, unpreventability, untreacherousness,
   unyieldingness, vis major