The Collaborative International Dictionary of English v.0.48:

Falseness \False"ness\, n.
   The state of being false; contrariety to the fact;
   inaccuracy; want of integrity or uprightness; double dealing;
   unfaithfulness; treachery; perfidy; as, the falseness of a
   report, a drawing, or a singer's notes; the falseness of a
   man, or of his word.
   [1913 Webster]

WordNet (r) 3.0 (2006):

falseness
    n 1: the state of being false or untrue; "argument could not
         determine its truth or falsity" [syn: falsity,
         falseness] [ant: the true, trueness, truth,
         verity]
    2: unfaithfulness by virtue of being unreliable or treacherous
       [syn: faithlessness, falseness, fickleness,
       inconstancy]
    3: the quality of not being open or truthful; deceitful or
       hypocritical [syn: insincerity, falseness, hollowness]
       [ant: sincerity]

Moby Thesaurus II by Grady Ward, 1.0:

186 Moby Thesaurus words for "falseness":
   Machiavellianism, Prospero, Punic faith, Tartuffery, Tartuffism,
   aberrancy, aberration, affectation, airiness, ambidexterity,
   apostasy, appearance, artfulness, artifice, bad faith,
   bamboozlement, barratry, befooling, bluffing, breach of faith,
   breach of promise, breach of trust, calculated deception, cant,
   circumvention, conning, craft, cunning, deceit, deceitfulness,
   deceiving, deception, deceptiveness, defectiveness, defrauding,
   delusion, delusiveness, dereliction, desertion, deviancy,
   disaffection, dishonesty, disloyalty, distortion, double-dealing,
   doubleness, doubleness of heart, dupery, duplicity, enmeshment,
   ensnarement, entanglement, entrapment, errancy, erroneousness,
   error, faithlessness, fallaciousness, fallacy, false appearance,
   false light, false piety, false show, falseheartedness, falsehood,
   falsity, fault, faultiness, fickleness, flaw, flawedness, flimflam,
   flimflammery, fond illusion, fooling, furtiveness, goody-goodiness,
   guile, hallucination, hamartia, heresy, heterodoxy, hoodwinking,
   hypocrisy, idealization, illusion, illusionism, illusionist,
   illusiveness, immateriality, improbity, inconstancy, indirection,
   infidelity, insidiousness, insincerity, kidding, low cunning,
   magic, magic act, magic show, magician, mala fides,
   mealymouthedness, mirage, misapplication, misconstruction,
   misdoing, misfeasance, misinterpretation, misjudgment, mummery,
   oiliness, outwitting, overreaching, peccancy, perfidiousness,
   perfidy, perversion, phantasm, pharisaicalness, pharisaism,
   pietism, pietisticalness, piety, piousness, prestidigitation,
   putting on, recreancy, religionism, religiosity, sanctimoniousness,
   sanctimony, seeming, self-contradiction, self-deception,
   self-righteousness, semblance, shiftiness, show, simulacrum, sin,
   sinfulness, sleight of hand, sneak attack, sneakiness, snivel,
   snow job, snuffle, song and dance, sorcerer, sorcery,
   specious appearance, spoofery, spoofing, subterfuge,
   surreptitiousness, swindling, tergiversation, treacherousness,
   treachery, trickiness, tricking, trothlessness, two-facedness,
   unactuality, unction, unctuousness, underhandedness, unfaith,
   unfaithfulness, unloyalty, unorthodoxy, unreality, unsteadfastness,
   unsubstantiality, untrueness, untruth, untruthfulness,
   victimization, vision, wile, willful misconception,
   wishful thinking, wrong, wrongness