insolubleness

noun

1. (uncountable)The quality or state of being insoluble; insolubility.

   “But that vve may the more diſtinctly conſider this grand argument, […] it vvill be convenient to obſerve, that it does, at once, both propoſe a queſtion, and contain an objection, grounded upon the ſurmiſed inſolubleneſs of that queſtion.”

   “All his occasional pangs of dubiousness as to the grand governing thing of all—the reality of the physical relationship—only recoiled back upon him with added tribute of both certainty and insolubleness.”