noun. The state or character of being uncertain.

noun. being unsettled or in doubt or dependent on chance

"And odd whiles the sounds to be as of great monsters; and the earth to shake under us; and other-whiles there to be a hush and only the steam about us, and somewhere in the distance and uncertainness a low piping of some steam cranny, very strange and lonesome-sounding."

quality  

doubt  doubtfulness  dubiousness  fortuitousness  improbability