irrelevance, irrelevancy - the lack of a relation of something to the matter at hand

quality - an essential and distinguishing attribute of something or someone; "the quality of mercy is not strained"--Shakespeare

impalpability, intangibility, intangibleness - the quality of being intangible

insubstantiality - lacking substance or reality

abstractness - the quality of being considered apart from a specific instance or object

unreality - the quality possessed by something that is unreal