What is Virtue?

Legal Definition
Virtue (Latin: virtus, Ancient Greek: ἀρετή "arete") is moral excellence. A virtue is a trait or quality deemed to be morally good and thus is valued as a foundation of principle and good moral being. Personal virtues are characteristics valued as promoting collective and individual greatness. The opposite of virtue is vice.
-- Wikipedia
Legal Definition
The phrase "hy virtue" differs in meaning from "under color." For instance, the proper fees are received by virtue of the offico; extortion is under color of the office. Any rightful act in office is by virtue of the office. A wrongful act in office may be under color of the office. Phil. Law, 380.
-- Black's Law Dictionary
Legal Definition
Effect; tenor.
-- Ballentine's Law Dictionary