QuestionsWhat makes something right?There are no objective values: our moral judgements are all false
What makes something right?Morality questioned

There are no objective values: our moral judgements are all false

The error theory (the argument from queerness)

John Leslie Mackie 1917 · 1981Evil makes belief in a God both all-powerful and wholly good incoherent.
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What it claims

There are no objective values, and our moral judgements, which claim them, are all false. Morality is not to be discovered: it is to be invented.

Why

Objective values would be very strange things, and moral codes vary too much to come from perceiving them.

The same idea through history
David Hume1751Hume writes that moral taste "gilds or stains" things with colours borrowed from our sentiments: the value we see in the world comes from us. Mackie appeals to this idea of projection.
John Leslie Mackie1977Mackie opens his book with "There are no objective values" and coins the name "error theory": unlike Ayer, he thinks our moral judgements do assert something, but something false. Morality has to be invented.
In short

"There are no objective values: our moral judgements are all false" is an argument by John Leslie Mackie (Ethics: Inventing Right and Wrong, ch. 1 (1977), 1977) on the question "What makes something right?" (answer: morality questioned). Its claim: There are no objective values, and our moral judgements, which claim them, are all false. Morality is not to be discovered: it is to be invented. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 3 objections, 3 of them with a documented reply, and the original text behind each premise, checked word for word.

Ethics: Inventing Right and Wrong, ch. 1 (1977)
Valid with an implicit premise

When we say "torturing a child for fun is wrong", we do not mean "I dislike it". We mean it is wrong for everyone, even for someone who thinks otherwise. Mackie grants this: our moral judgements claim to describe objective values. But he thinks no such values exist. They would be far too strange, and moral disagreements are well explained without them. Conclusion: our moral judgements are all mistaken, rather like sentences about witches. This is not a call to do anything at all: for Mackie, morality is not discovered, it has to be invented.

P1Our ordinary moral judgements claim objectivity: "it is wrong" means it is wrong for everyone, whatever anyone thinks. If those objective values do not exist, these judgements are therefore false.
P2The argument from relativity: moral codes vary a great deal between societies, and these differences are better explained by ways of life than by a more or less accurate perception of objective values. People approve of monogamy because they live in a monogamous society, rather than the other way round.
P3The argument from queerness: objective values would be very strange things, unlike anything else in the universe. They would contain an order in themselves ("do this"), and a special faculty of perception would be needed to know them.
P4 · implicit premiseOne should not accept the existence of such strange things when a simpler explanation (our ways of life, our feelings projected onto the world) accounts for our beliefs.
So there are no objective values, and our moral judgements, which claim them, are all false. Morality is not to be discovered: it is to be invented.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where objective values are strange, where we could do without them to explain our beliefs, and where they exist all the same. This is the realists' position: the world is not obliged to be simple, and many true things are strange.
P2 and P3 show that objective values would be strange and that we do not need them to explain our beliefs; P4 says we should then not believe in them; this yields "there are no objective values". P1 adds the second step: since our judgements claim such values, they are false. The debate turns on P3 (are values any stranger than logical truths?) and on P1 (do our judgements really claim this strong objectivity?).
Analogy. In the sixteenth century people said "this woman is a witch". The sentence meant something precise: that she had supernatural powers. Since witches do not exist, all those sentences were false, even if the speakers were sincere. For Mackie, "lying is wrong" is in the same position: the sentence asserts something that does not exist. The difference, he says, is that we still need rules to live together: so we have to invent them.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

R
Russ Shafer-Landau ("companions in guilt") 2003 · attacks premise 3

If we reject moral values because they would be "strange", we must reject many other things: the truths of logic and mathematics, or the rules that say what it is reasonable to believe. They too are independent of us, invisible, and binding on us. Yet nobody judges them non-existent. Moral values are no stranger than they are.

Mackie replies
J. L. Mackie 1977 · Mackie's reply in advance (same chapter)
Mackie raises this defence himself: necessity, causation, identity or number would pose the same problem. His answer: these notions too must be given an empiricist account, starting from experience; and if this succeeds for them, it still does not rescue values that would contain an order.
T
Terence Cuneo 2007
The price is too high. Reasons for belief ("you ought to believe what the evidence shows") are normative facts exactly like moral facts. If Mackie is right, they do not exist either, and then we have no reason to believe the error theory itself. The position saws off the branch it sits on.
The debate goes on (our summary) Present-day error theorists (Joyce, Olson) reply that reasons for belief can depend on our goals, which is not the case for moral duties, which claim to bind us even against our goals. The debate remains open.
C
Common objection attacks the conclusion

If all moral judgements are false, we should stop saying that slavery was wrong, as we stopped talking about witches. Nobody can live that way, not even Mackie, who then writes a whole book of ethics. The theory is refuted in practice.

Mackie replies
summary: their text is not yet in our corpus
J. L. Mackie 1977 · The answer in the title: inventing right and wrong
The error theory concerns what values are, not what we should do. It does not force us to give up morality, but to see it differently: a set of rules that humans build to live together, which can be discussed and improved. That is what Mackie does in the second part of the book.
R
Richard Joyce 2001 · Fictionalism
Joyce goes further: we can go on saying "stealing is wrong" without strictly believing it, as we talk about the characters in a novel. Keeping this fiction is useful, because it helps us keep our commitments when temptation is strong.
The debate goes on (our summary) Critics ask whether a fiction one knows to be false can still hold someone back at the moment of temptation. Other error theorists, called "abolitionists" (Garner), propose instead to do without moral vocabulary.
William Lane Craig (the moral argument for God) 1997 · attacks premise 4

It is more certain that gratuitous cruelty is really wrong than any philosophical thesis about what is "strange". If we must choose, it is better to keep objective values and look for what grounds them: for Craig, that is God. See the argument "The moral law points to a lawgiver".

Mackie replies
J. L. Mackie 1982
Mackie grants the link: objective values, if they existed, would make the existence of a god more probable. But he draws the opposite conclusion: this link is one more reason to think they do not exist, since our values have a natural explanation.
The debate goes on (our summary) So both sides agree on one point: objective values and God go well together. They part ways over what is more certain: moral evidence (Craig) or a world with nothing "strange" in it (Mackie). Atheist realists such as Wielenberg reject this choice: in their view, objective values exist without God.
What today's voices say
Criticize it
William Lane CraigHe criticizes Michael Ruse for using moral outrage against God while holding that objective morality is an illusion.
Trent HornHe turns Mackie's point around: if objective moral facts are real, one should give up atheism rather than morality.