Duty

In plain terms

Some things are required whether or not they help, and whether or not you feel like it. Keeping a promise when it has become inconvenient. Telling the truth when a lie would go unnoticed. Not using someone even when nobody would be harmed.

That is the intuition duty names, and its force is that it holds against calculation. An ethics of consequences says a promise may be broken when breaking it produces more good. An ethics of duty says the promise binds, and that a person who keeps promises only when they pay has not understood what a promise is.

The cost of that firmness is the hard cases, and they are genuinely hard. Every duty-based system eventually meets a situation where doing the required thing produces a disaster, and has to say something.

As a philosopher would put it

Kant grounds duty in the categorical imperative: act only on a maxim you could will as a universal law, and treat humanity always as an end and never merely as a means. Its bindingness comes from rational agency itself, which is why it is categorical rather than hypothetical - not if you want X, do Y, but do Y.

Acting from duty is distinguished from acting in conformity with it. The shopkeeper who is honest because dishonesty is bad for trade acts rightly and not from duty, and only the second has moral worth - a claim critics have found either profound or repellent since Schiller's satire on it.

Ross's alternative is more usable: a plurality of prima facie duties - fidelity, reparation, gratitude, justice, beneficence, self-improvement, non-maleficence - none absolute, each capable of being outweighed, with judgement required to determine the actual duty in a case. That gives up systematic derivation and keeps the phenomenology, which most working ethics now follows.

What is actually disputed

Whether duties can conflict, and what happens when they do.

Absolutist systems hold that a genuine duty admits no exception, which is what gives it force and produces the standard objection - Kant's own conclusion that one may not lie to a murderer at the door has been used against him for two centuries, and his defenders remain divided about whether the position is his considered one.

Pluralist systems accept conflict and rank duties by judgement, which is realistic and abandons the systematic character that made duty attractive. Ross admits that determining the actual duty in a case is not a matter of proof.

The deeper challenge comes from the other side. Consequentialists argue that a duty producing disaster cannot be a duty, and that rule-worship is what remains of a system when its point is forgotten. Anscombe replies that obligation-talk is the residue of a divine lawgiver no longer believed in, and that without one the concept has no work to do.