Tenable /(tĕn"ȧ*b'l)/

Ten·a·ble

Tenable

a.
  1. Capable of being held, maintained, or defended, as against an assailant or objector, or against attempts to take or process; as, a tenable fortress, a tenable argument.
    If you have hitherto concealed his sight, Let it be tenable in your silence still.
    I would be the last man in the world to give up his cause when it was tenable.