Treasonableness is the quality of being reasonable or justifiable. There are several synonyms that can be used to describe this quality, including rationality, soundness, fairness, logic, sensibleness, and validity. Treasonableness can also be expressed as reasonableness, which suggests that something is sensible, justified, and pragmatic. Other suitable synonyms include propriety, balance, and objectivity, which all signify a sense of fairness and impartiality. Ultimately, when we describe something as treasonable, we are indicating that it is grounded in sound reasoning and ethical principles, and that it follows an appropriate and just course of action.