tenable

1. (of a theory, argument, etc.) capable of being maintained or justified; well-foundedExamples: "Back in the 1800s, many did not consider Darwin's theory of evolution to be tenable at all."; "Modern war rests on industry, and its evolution has all but abolished the "non-combatant," emptied the old idea of "innocent" trade of meaning, and made even of neutrality a barely tenable status."; "Fitting into a tenable social position among other people requires not only the ability to simultaneously assess the nature of relationships with each person individually but also the ability to comprehend the indirect relational consequences of actions for connected relationships."usually

2. (military) Capable of being defended against assault or attack; defensibleExamples: "The island of Melos undoubtedly fell within his general conceptions of tenable empire for Athens."