 [T]here are some modern systems, according to which virtue consists in propriety; or in the suitableness of the affection from which we act, to the cause or object which excites it … None of those systems either give, or even pretend to give, any precise or distinct measure by which this fitness or propriety of affection can be ascertained or judged of. That precise and distinct measure can be found nowhere but in the sympathetic feelings of the impartial and well-informed spectator. (TMS 346)