Source : Webster's Revised Unabridged Dictionary (1913)

Sinless \Sin"less\, a.
   Free from sin. --Piers Plowman. -- {Sin"less*ly}, adv. --
   {Sin"less*ness}, n.

Source : WordNet®

sinlessness
     n : the state of being free from sin or moral wrong; lacking a
         knowledge of evil [syn: {purity}, {innocence}]