1) Plausibility 2) Plausibleness 3) Reasonableness 4) Tenableness 1) Tenableness 
• (n.) The quality or state of being tenable; tenableness.
Ten`a·bil'i·ty noun The quality or state of being tenable; tenableness. 
tenable, tenability, tenableness That which can be held, defended, or maintained [to hold, to grasp, to have].
tenableness noun the quality of being plausible or acceptable to a reasonable person; `he questioned the tenability of my claims`