Source : Webster's Revised Unabridged Dictionary (1913)

Artlessness \Art"less*ness\, n.
   The quality of being artless, or void of art or guile;
   simplicity; sincerity.

Source : WordNet®

artlessness
     n 1: the quality of innocent naivete [syn: {innocence}, {ingenuousness},
           {naturalness}]
     2: ingenuousness by virtue of being free from artful deceit
        [ant: {artfulness}]