based on sound reasoning or evidence; "a reasonable argument"; "well-founded suspicions"
If you say that an argument, point of view, or situation is tenable, you believe that it is reasonable and could be successfully defended against criticism. This argument is simply not tenable untenable. a belief, argument etc that is tenable is reasonable and can be defended successfully (tenir; TENANT)
Capable of being held, naintained, or defended, as against an assailant or objector, or againts attempts to take or process; as, a tenable fortress, a tenable argument