tenable

adjective3

1. •
   capable of being maintained or justified; well-founded

   • Back in the 1800s, many did not consider Darwin's theory of evolution to be tenable at all.
2. •
   Capable of being defended against assault or attack; defensible

   • The island of Melos undoubtedly fell within his general conceptions of tenable empire for Athens. — 1850
3. •
   (formal) Fit for habitation, similar, or related use.

   • In February, 1679, he was admitted "a planter" of the town and a home lot was granted him "on condition that it should have a tenable house built upon it within two years. — 1679