The Collaborative International Dictionary of English v.0.48:

Immateriality \Im`ma*te`ri*al"i*ty\, n.; pl. Immaterialities.
   [Cf. F. immat['e]rialit['e].]
   The state or quality of being immaterial or incorporeal; as,
   the immateriality of the soul.
   [1913 Webster]

WordNet (r) 3.0 (2006):

immateriality
    n 1: complete irrelevance requiring no further consideration
         [ant: materiality]
    2: the quality of not being physical; not consisting of matter
       [syn: immateriality, incorporeality] [ant: corporality,
       corporeality, materiality, physicalness]

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "immateriality":
   Masan, Prospero, airiness, airy nothing, apparition, appearance,
   astral, astral spirit, banshee, bodilessness, concealment, control,
   delusiveness, departed spirit, disappearance, disassociation,
   disconnection, discreteness, disembodied spirit, disjunction,
   disjuncture, dissociation, duppy, dybbuk, eidolon, ethereality,
   fallaciousness, false appearance, false light, false show,
   falseness, fineness, flimsiness, form, ghost, grateful dead, guide,
   hant, haunt, idealization, idolum, illusionism, illusionist,
   illusiveness, impalpability, imperceptibility, impertinence,
   imponderability, inapplicability, inappositeness, inconnection,
   inconsequence, inconsequentiality, inconsiderableness, incorporeal,
   incorporeal being, incorporeality, incorporeity, independence,
   indifference, indiscernibility, ineffectuality, inferiority,
   insignificance, insolidity, insubstantiality, intangibility,
   invisibility, irrelation, irrelevance, larva, lemures, littleness,
   low priority, magic, magic act, magic show, magician, manes,
   marginality, materialization, mistiness, negligibility,
   nonappearance, oni, pettiness, phantasm, phantasma, phantom,
   picayune, picayunishness, pokiness, poltergeist, presence,
   prestidigitation, puniness, rareness, rarity, revenant,
   secondariness, secrecy, seeming, semblance, separateness, shade,
   shadow, shape, show, shrouded spirit, simulacrum, sleight of hand,
   slightness, smallness, sorcerer, sorcery, specious appearance,
   specter, spectral ghost, spirit, spook, sprite, subtility,
   subtilty, subtlety, tenuity, tenuousness, the invisible,
   the unseen, theophany, thinness, unactuality, unconcreteness,
   unconnectedness, unimportance, unimpressiveness, unnoteworthiness,
   unperceivability, unreality, unrelatedness, unseeableness,
   unsolidity, unsubstantiality, unsubstantialness, vagueness,
   viewlessness, vision, walking dead man, wandering soul, wraith,
   zombie