Metaethics

What it asks

Two people disagree about whether an act was wrong. Before asking who is correct, ask what they are disagreeing about.

If moral claims describe facts, the disagreement is like one about chemistry and at most one party is right. If they express attitudes, it is more like a clash of preferences, and calling one party mistaken needs explaining. If they issue instructions, it is neither.

Everything in the branch follows from that one question, and the striking thing is that the answer constrains moral practice much less than either side usually expects.

The recurring problems

Is and ought. Hume observed that arguments slide from statements about how things are to statements about what ought to be without anything licensing the move. The observation is three lines long and has never been fully answered.

The open question. Moore argued in 1903 that for any natural property you identify with goodness, it remains a sensible question whether things with that property are good - which suggests goodness is not that property. The argument has known weaknesses and keeps working anyway.

Queerness. If moral facts existed they would be unlike anything else: facts that of themselves give anyone a reason to act. Mackie argued in 1977 that nothing is like that, so there are no moral facts and all moral claims are false.

The Frege-Geach problem. If saying stealing is wrong expresses disapproval rather than stating a fact, what does IF stealing is wrong, then getting your brother to steal is wrong express? No disapproval is expressed there, and the argument is plainly valid. Answering this has occupied expressivists for sixty years.

How it developed

Hume supplied the is-ought gap and the view that morality rests on sentiment rather than reason. Kant supplied the opposite: that moral requirements are demands of reason itself.

The field became distinct with Moore's Principia Ethica in 1903, which argued that good is a simple non-natural property that cannot be defined.

The logical positivists drew the sharper conclusion. If a statement is meaningful only when it can be verified, moral statements are not statements at all. Ayer's emotivism in 1936 held that they express feeling; Stevenson added that they aim to change attitudes; Hare held they are prescriptions. For thirty years, metaethics displaced normative ethics almost entirely - it seemed pointless to argue about what is right before knowing what such an argument could be.

Mackie's error theory in 1977 combined a realist reading of moral language with a denial that anything answers to it. Since then the sophisticated forms of expressivism have tried to earn back everything realism offers - truth, argument, error - without moral facts, and the dispute has become extremely technical.

The positions within it

Moral realism in naturalist and non-naturalist versions; error theory; emotivism, prescriptivism and quasi-realism; constructivism; relativism. All are in the Schools section.

The useful axis is not realism against anti-realism but whether moral claims aim at truth, and whether anything makes them true.

Where it stands now

Quasi-realism and constructivism have narrowed the gap between the camps so far that whether a real dispute remains is itself debated.

The pressure now is empirical and comparative. Evolutionary accounts of moral judgement raise the question of whether a faculty shaped for cooperation could be tracking moral truth. And work on moral disagreement across cultures has made relativism a live position again rather than the beginner's error it was treated as for most of the twentieth century.