In its use in Jurisprudence, this word is the correlative of right. Thus,wherever there exists a right in any person, there also rests a corresponding duty upon some other person or upon all persons generally. But it is also used, in a wider sense,to designate that class of moral obligations which lie outside the jural sphere; such,namely, as rest upon an imperative ethical basis, but have not been recognized by the law as within its proper province for purposes of enforcement or redress. Thus, gratitude towards a benefactor is a duty, but its refusal will not ground an action. In this meaning “duty” is the equivalent of “moral obligation,” as distinguished from a “legal obligation.” See Kentucky v. Dennison, 24 How. 107, 16 L. Ed. 717; Harrison y. Bush,5 El. & Bl. 349. As a technical term of the law. “duty” signifies a thing due; that which is due from a person; that which a person owes to another. An obligation to do a thing. A word of more extensive signification than “debt,” although both are expressed by the same Latin word “debitum.” Beach v. Boynton, 20 Vt 725, 733.But In practice it is commonly reserved as the designation of those obligations of performance, care, or observance which rest upon a person In an official or fiduciary capacity ; as the duty of an executor, trustee, manager, etc.It also denotes a tax or impost due to the government upon the Importation or exportation of goods.
“The constitutions of most of our States assert that all power is inherent in the people; that… it is their right and duty to be at all times armed.” Thomas Jefferson (1977). “The Portable Thomas Jefferson”, p.458, Penguin
“But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security.” The Declaration of Independence [excerpt]