Overview – Metaethics

A level metaethics is about what moral judgements – e.g. “murder is wrong” – mean and what (if anything) makes them true or false.

The syllabus covers 5 metaethical theories. These theories can be categorised as either realist or anti-realist theories.

  • Moral realism: There are mind-independent, external moral properties and facts – e.g. “murder is wrong” is a moral fact because the act of murder has the moral property of wrongness
  • Moral anti-realism: Mind-independent moral properties and facts do not exist.

The theories can be further categorised as either cognitivist or non-cognitivist theories (cognitivism/non-cognitivism also crops up in religious language as well as moral language).

  • Cognitivism: Moral judgements express cognitive mental states – i.e. beliefs, aim to describe reality, and can be true or false
    • E.g. “Murder is wrong”
  • Non-cognitivism: Moral judgements express non-cognitive mental states, do not aim to describe reality, and are not capable of being true or false
    • E.g. “Boo! Murder!” or “Don’t torture animals!”

The following table categorises the 5 metaethical theories according to whether they are realist or cognitivist:

Moral realism Moral anti-realism

Having these two sets of categories (realism/anti-realism and cognitivism/non-cognitivism) can make it a bit confusing because there is overlap between the categories. For example, all non-cognitivist theories are anti-realist theories but not all cognitivist theories theories are realist theories.

So, it’s important to be clear on the differences between what the categories are about:

  • Realism/anti-realism is about whether or not mind-independent moral properties exist
  • Cognitivism/non-cognitivism is about what people mean when they make moral judgements

The theories are linked with each other to some degree. For example, the arguments against naturalism are the same arguments in favour of non-naturalism, and the arguments against non-naturalism are the same arguments in favour of error theory.

Realist theories

Realist metaethical theories argue that mind-independent moral properties – such as ‘right’, ‘wrong’, ‘good’, and ‘bad’ exist.

These moral properties give rise to moral facts, such as “murder is wrong”. A realist would say murder has the property of wrongness in the same way grass has the property of greenness.

But there is disagreement among realists as to what these mind-independent moral properties actually are:

  • Ethical naturalism says moral properties are natural properties
  • Ethical non-naturalism says moral properties are non-natural properties

Both ethical naturalism and ethical non-naturalism are cognitivist theories: they agree that moral judgements express beliefs that are capable of being true or false.

Ethical naturalism

Ethical naturalism says that moral judgements are beliefs that are intended to be true or false (cognitivism) and that moral properties exist (realism) and are natural properties.

Natural properties are ordinary, physical properties. Pain and pleasure, for example, are natural properties of the brain – a physical thing.

So, according to ethical naturalism, “murder is wrong” expresses a belief that murder is wrong – where ‘wrong’ refers to a natural property.

It’s a reductionist theory: it says moral properties can be reduced to natural properties. These properties exist and are mind-independent. Hence, ethical naturalism is a moral realist theory.

Utilitarianism is an example of a naturalist ethical theory. It says ‘good’ can be reduced to pleasure, and ‘bad’ can be reduced to pain.

Problems for ethical naturalism:

Ethical non-naturalism

Ethical non-naturalism says that moral judgements are beliefs that are intended to be true or false (cognitivism) and that moral properties exist (realism) but are non-natural properties.

So, according to ethical non-naturalism, “murder is wrong” expresses a belief that murder is wrong – where ‘wrong’ refers to a non-natural property.

One way to think about non-natural properties is as non-physical properties. These non-natural moral properties cannot be reduced to anything simpler. They are basic.

G.E. Moore: Principia Ethica

The naturalistic fallacy:

Moore’s book begins with criticisms of ethical naturalism.

He invents the term ‘Naturalistic fallacy’ to describe the fallacy (i.e. bad reasoning) of equating goodness with some natural property. His main arguments for the naturalistic fallacy are:

  • Moral properties may be correlated with natural properties, but are not identical to them. For example, having a heart is correlated with also having kidneys, but hearts are not the same thing as kidneys. Similarly, happiness may often accompany morally good actions, but they are not the same thing.
  • Moore’s ‘open question’ argument: if goodness and pleasure are the same thing, it wouldn’t make sense to ask ‘is pleasure good?’, because it would basically be like asking ‘is pleasure pleasure?’. But because the question ‘is pleasure good?’ does make sense, this proves that pleasure and good are not the same thing.
    • Reply to open question argument: It makes sense to ask ‘is water H2O?’ even though they refer to the same thing. The fact that this question does make sense does not prove that water and H2O are two separate things. So how can Moore’s argument (which follows the same format) prove that goodness and pleasure are two separate things?

Moore argues that moral properties cannot be reduced to anything simpler, such as pain or pleasure. Moral properties are basic.

Moore’s Intuitionism:

Having argued against ethical naturalism, Moore sets out his own version of ethical non-naturalism, which he calls intuitionism.

We might ask Moore: if moral properties are non-natural properties, how do we know about them?

It’s no mystery how we know about natural properties, such as blueness, roundness, or largeness. But non-natural properties are more difficult to explain – they’re not like ordinary physical properties that can be scientifically investigated.

Moore’s response to this problem is intuition. He argues that, via the faculty of rational intuition, we can directly reflect on the truth of moral judgements such as “murder is wrong”. The truth/falsehood of such moral judgements is said to be self evident.

Problems for ethical non-naturalism:

Anti-realist theories

Anti-realist metaethical theories argue that mind independent moral properties do not exist. So, there are no such things as true moral facts.

The syllabus looks at 3 anti-realist metaethical theories:

  • Error theory says moral judgements are cognitive statements but properties don’t exist
  • Emotivism says moral judgements are non-cognitive statements that express feelings of approval or disapproval
  • Prescriptivism says moral judgements are non-cognitive statements that are intended as instructions

Error theory

Error theory says that moral judgements are beliefs that are intended to be true or false (cognitivism). However, error theory also says that moral properties don’t exist (anti-realism) and so these moral judgements are all false.

So, according to error theory, the statement “murder is wrong” expresses a belief that murder is wrong – but ‘wrong’ refers to a non-existent property and so the statement is false. It’s like saying “grass is blellow” – ‘blellow’ is a made up colour that doesn’t exist and so “grass is blellow” is a false statement.

Since moral properties don’t exist according to error theory, it claims that all moral propositions – e.g. “murder is wrong” – are false. So, not only is “murder is wrong” false but “murder is good” is also false because ‘goodness’ doesn’t exist either.

J.L. Mackie: Ethics: Inventing Right and Wrong

Arguments for cognitivism

Mackie’s book starts with various arguments in favour of cognitivism generally.

Moral philosophy, he argues, has tended to assume objective moral values (e.g. Plato and Kant) – i.e. that moral judgements are objectively true or false.

Not only that, ordinary language assumes cognitivism as well. To illustrate this, Mackie uses the example of someone facing the moral dilemma of whether to engage in research related to bacteriological warfare. In trying to resolve this dilemma, you don’t ask how you feel about it – you ask whether such action is wrong in itself.

Having established that moral judgements are cognitive and thus aim to be true or false, Mackie next turns his attention to the nature of moral properties. Mackie argues that such moral properties do not exist (i.e. he argues for moral anti-realism).

The argument from relativity

Mackie’s first argument for anti-realism starts by pointing out that there are variations in moral beliefs between cultures (and between the same culture at different time periods).

For example: Some cultures are polygamous, other cultures think this is wrong. Some cultures think eating certain animals is wrong, other cultures eat those animals. And historically, many cultures have kept slaves, but most modern cultures think this is wrong.

If moral realism is correct, there would only be one objectively correct answer to all of these issues. Why, then, is there so much disagreement on these issues? Cultures that are independent of each other tend to form completely different moral practices and beliefs. We can explain this disagreement in one of two ways:

  • One culture has, for some reason, discovered objective moral reality while the other hasn’t
  • Each culture has different conditions and a different way of life and has developed their own moral beliefs in response to that

Mackie’s argument is that the second option is the more plausible account. If moral realism were true, you wouldn’t expect to see such divergent moral beliefs.

To put it another way, if there were objective moral properties and facts (i.e. if moral realism were true), you would expect every culture to eventually discover these moral facts in a similar way to how every culture has discovered other objective truths such as “1+1=2”.

The argument from queerness

Mackie’s main argument for moral anti-realism is that moral properties would have to be very strange (or ‘queer’, to use Mackie’s term). His reasons:

  • Epistemically queer: If mind-independent moral properties exist, then it is a total mystery how we would acquire knowledge of them. Whereas natural knowledge can be explained naturally, moral knowledge can’t be explained in the same way and instead requires spooky hypotheses such as Moore’s intuitionism
  • Metaphysically queer: If mind-independent moral properties exist, they must be metaphysically unlike anything else we have experience of. For example, ‘good’ things would need to somehow have to-be-doneness built into them and ‘bad’ things would have not-to-be-doneness built into them. But it’s not clear how objective, physical, objects could relate to human motivations in this way (scientifically, metaphysically, or otherwise).

Note: Mackie’s arguments here are primarily directed at the idea of non-natural moral properties. 

Another way of getting at the metaphysical weirdness is to question how moral facts relate to natural facts. Imagine someone stealing from a shop. Then imagine someone stealing from a shop and that this action has the property of wrongness. What’s the difference between the two cases? What does the property of ‘wrongness’ add to the natural facts of the situation? It’s not clear.

Mackie argues that the queerness of moral properties – both epistemic and metaphysical – is evidence that moral properties do not exist.

Problems for error theory


Non-cognitivists believe that moral judgements such as “murder is wrong” express non-cognitive mental states. Non-cognitive statements do not aim to describe reality and so are not supposed to be taken as either true or false. Non-cognitivists do not believe in the existence of moral properties that would make moral statements true or false and so all non-cognitivist metaethical theories are also anti-realist theories.

The syllabus lists two non-cognitivist metaethical theories: Emotivism and prescriptivism.


Emotivism says that moral judgements express (non-cognitive) feelings of approval or disapproval.

So, according to emotivism, when someone says “murder is wrong!”, what they really mean is “boo! murder!”

(By the way, “boo!” here is like when people “boo!” at a football match, not “boo!” like when you jump out at someone to scare them. This doesn’t really come across in text…)

Similarly, when someone says “giving money to charity is good”, what they are really expressing is “hooray! Giving money to charity!”

Notice how none of these attitudes are capable of being true or false. They are just expressions of approval or disapproval – not beliefs. Hence, emotivism is a non-cognitivist theory.

Hume: Treatise of Human Nature

Before getting on to Hume’s argument for emotivism specifically, Hume provides two arguments for the view that moral judgements are not judgements of reason – i.e. that moral judgements are non-cognitive.

(you can use these arguments to argue against any of the cognitivist theories: naturalism, non naturalism and error theory)

Moral judgements motivate action

According to Hume, judgements of reason – e.g. a belief that grass is green – don’t motivate us to act in any way. Instead, it’s emotions and desires that motivate us to act. For example, my desire to drink beer might motivate me to seek out beer.

According to Hume, moral judgements seem more like the beer-drinking example because they motivate action. For example, my belief that “murder is wrong” will motivate me not to murder or my belief that “giving money to charity is good” will motivate me to give money to charity.

So, Hume’s argument here is essentially:

  • Moral judgements can motivate action
  • Judgements of reason cannot motivate action
  • Therefore, moral judgements are not judgements of reason
    • (In other words, moral judgements are non-cognitive)
Hume’s fork (again)

If you remember Hume’s fork from epistemology, Hume argued there are just two types of judgements of reason: relations of ideas and matters of fact.

Applying Hume’s fork to moral judgements, he argues:

  • Moral judgements are not relations of ideas
  • Moral judgements are not matters of fact
  • Therefore, moral judgements are not judgements of reason
    • (Again, in other words, moral judgements are non-cognitive)
The is/ought problem

Hume argues that you cannot logically derive ought statements from statements about what is.

For example, to say “you shouldn’t torture animals because it hurts them!” derives a statement about what ought to be (you shouldn’t torture animals) from a statement about what is (torturing animals causes pain). Hume says this does not – and could not – follow.

This idea is closely related to the naturalistic fallacy that Moore argues.

And another closely related idea is the fact/value distinction. For example:

  • Fact: Smith murdered Jones
  • Value: Murder is wrong

Non-cognitivists argue that facts and values are two completely separate things. Facts are true in virtue of how the world is whereas values express attitudes towards facts.

So, since ought statements cannot be reasoned from is statements, Hume argues that:

“morality is more properly felt than judg’d of.”

Hume’s arguments here have been interpreted to support emotivism – the view that moral judgements express attitudes, not facts.

A.J. Ayer: Language, Truth and Logic
The verification principle

(The verification principle also comes up in religious language)

The verification principle: a statement only has meaning if it is either:

  • An analytic truth (e.g. “a triangle has 3 sides”)
  • Empirically verifiable (e.g. “water boils at 100c”)

Any statement that does not fit these descriptions is meaningless, according to the verification principle.

Ayer argues that moral judgements fail the verification principle. Firstly, “murder is wrong” is clearly not an analytic truth. Ayer also argues that “murder is wrong” is not empirically verifiable either – both on the naturalist and non-naturalist interpretations:

  • Naturalism would argue that we could prove that murder causes pain, anger, etc. However, Ayer argues that this is not the same as proving murder is wrong. Hence, Ayer rejects naturalism: We can empirically verify that murder causes pain, say, but we cannot empirically verify that murder is wrong.
  • Ayer also argues that there is no way to empirically verify the presence of non-natural properties. Even if “murder is wrong” did possess the non-natural property of wrongness, how could we ever prove this? It’s not empirically verifiable, nor is it an analytic truth. Hence, Ayer also argues against non-naturalism: The existence of non-natural properties cannot be empirically proven.

So, moral judgements are not analytic truths, nor are they empirically verifiable. Therefore, according to the verification principle, they are meaningless.

Instead of expressing factual statements about the external world, Ayer concludes that moral judgements simply express feelings of approval or disapproval and seek to evoke the same feelings in others:

“If I say to someone, “you acted wrongly in stealing that money” […] I am simply evincing my moral disapproval of it. It is as if I had said, “You stole that money,” in a peculiar tone of horror.”

So, like Hume, Ayer is an emotivist.


Prescriptivism says that moral judgements express (non-cognitive) instructions that aim to guide behaviour.

So, according to prescriptivism, when someone says “murder is wrong!”, what they really mean is “don’t murder people!”

When you instruct someone to do something – e.g. “shut the door” – you are not expressing a belief that is capable of being true or false. Hence, emotivism is a non-cognitivist theory.

R.M. Hare: The Language of Morals

Hare says there are two types of prescriptive meaning:

  • Imperatives: tell someone to do something – e.g. “shut the door” or “go away”
  • Value judgements: praise or criticise something – e.g. “that’s good” or “that’s bad”

Hare says emotivism misses the force of moral judgements. They don’t just express what you feel and try to get others to feel the same (as Ayer claims), they’re also prescriptions for what you ought to do. So, moral judgements are both value judgements and imperatives.

Hare further argues that ‘good’ and ‘bad’ are more than just descriptions. We assume a set of standards – e.g. a ‘good’ teacher is one who can explain ideas clearly and keep the students interested – and then praise or criticise according to these standards. When we say a person is ‘good’ in the moral sense we use the general standards that apply to someone as a person. However, Hare argues, these standards have to be adopted by us. There is nothing about the facts themselves that establish one set of standards as correct.

Hare describes the key features of the word ‘good’:

  • It is used to praise and provide guidance for how to act
  • It assumes a set of standards
  • If two things are identical, they must both be good or bad. It wouldn’t make sense for one thing to be good and an identical thing to be bad

Problems for non-cognitivism

Moral argument and reasoning

(note: the following argument applies to non-cognitivist theories (i.e. prescriptivism and emotivism) but not cognitivist theories (e.g. error theory))

Non-cognitivism appears to be at odds with how we typically use moral judgements.

We often use moral judgements as part of moral reasoning. For example:

  1. If murder is wrong, then you shouldn’t murder people
  2. Murder is wrong
  3. Therefore, you shouldn’t murder people

This seems like a sound argument. The conclusion follows logically from the premises. And if the premises are true then the conclusion must also be true.

But if non-cognitivism is true, the argument above isn’t actually sound. Prescriptivists, for example, say that what people really mean when they say “murder is wrong” is something like “don’t murder people!”

So, the argument above is something more like:

  1. If “don’t murder people!”, then you shouldn’t murder people
  2. “Don’t murder people!”
  3. Therefore, you shouldn’t murder people

But this argument isn’t sound, because the premises aren’t true.

In fact, it’s a key claim of the non-cognitivist theories emotivism and prescriptivism that moral judgements cannot be true or false. Premise 2, for example, is neither true nor false.

So, if non-cognitivism is true, the first argument is not a sound argument. But it clearly is a sound argument. Therefore, non-cognitivism is false.

Mackie’s arguments for cognitivism

See error theory section above.

Problems for anti-realism

(note: the following problems apply to all anti-realist theories (i.e. error theory, prescriptivism and emotivism))

Moral nihilism

If moral anti-realism is true, it can be argued that this leads to moral nihilism: the view that no actions are inherently wrong. There’s nothing true about moral judgements such as “murder is wrong”. This then raises the question of why anyone should bother to be moral at all.

Non-cognitivists can respond that just because there’s no inherent right or wrong, people still have moral attitudes and feelings. And the realisation that moral values are just expressions of feelings doesn’t mean we should (or could) stop having these moral feelings.

It’s also somewhat self-defeating to be a moral nihilist according to non-cognitivism. After all, living as if there are no moral values is itself an expression of a certain attitude or feeling.

Cognitivist anti-realist theories (i.e. error theory) have a harder time responding to the charge of moral nihilism. One response could be to just accept the charge of moral nihilism and argue that, though undesirable, this doesn’t make error theory any less true.

There may also be practical reasons to behave as if some moral judgements are true. For example, if you were always stealing from your friends, chances are they wouldn’t remain friends with you for very long.

Moral progress

Our moral values have changed over time. For example, it was considered morally acceptable to keep slaves back in the time of Plato but it’s not today.

If we accept that such changes are examples of moral progress, then we can make an argument along these lines:

  1. If moral anti-realism is true, then there would be no moral progress
  2. But there has been moral progress
  3. Therefore moral anti-realism is false

This is a somewhat question-begging argument though. The second premise essentially assumes the conclusion. Why should the anti-realist accept there’s been objective moral progress when he doesn’t accept the existence of objective morality in the first place?

However, we can define moral progress in less question-begging ways. For example, we could argue that our morality has become more consistent over time, or that we have adapted our moral values in response to greater knowledge of the facts.

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