Non-cognitivism is the meta-ethical view that ethical sentences do not express propositions (i.e., statements) and thus cannot be true or false (they are not truth-apt).
A noncognitivist denies the cognitivist claim that "moral judgments are capable of being objectively true, because they describe some feature of the world.
Emotivism, associated with A. J. Ayer, the Vienna Circle and C. L. Stevenson, suggests that ethical sentences are primarily emotional expressions of one's own attitudes and are intended to influence the actions of the listener.
Prescriptivists interpret ethical statements as being universal imperatives, prescribing behavior for all to follow.
Other forms of non-cognitivism include Simon Blackburn's quasi-realism and Allan Gibbard's norm-expressivism.
As with other anti-realist meta-ethical theories, non-cognitivism is largely supported by the argument from queerness: ethical properties, if they existed, would be different from any other thing in the universe, since they have no observable effect on the world.
In a descriptive sentence, if one premises that "red is a number" then according to the rules of English grammar said statement would be false.
is uttered, and this premise is negated (by the fact of a person being murdered), the speaker is not to change his sentence upon observation of this into "kill other people!
Some cognitivists argue that some expressions like "courageous" have both a factual as well as a normative component which cannot be distinguished by analysis.
Many moral statements are de facto uttered as recommendations or commands, e.g. when parents or teachers forbid children to do wrong actions.
Actors cannot externalize their responsibility and freedom of will towards some moral truth in the world, virtuous people do not need to wait for some cognition to choose what's right.
Prescriptivism is also supported by imperative logic, in which there are no truth values for imperatives, and by the idea of the naturalistic fallacy: even if someone could prove the existence of an ethical property and express it in a factual statement, he could never derive any command from this statement, so the search for ethical properties is pointless.
If John gives to the poor, takes care of his sick grandmother, and is friendly to others, and these are what inspire the speaker to think well of him, it is plausible to say, "John is a good person because he gives to the poor, takes care of his sick grandmother, and is friendly to others".
Consider the following examples: Attempts to translate these sentences in an emotivist framework seem to fail (e.g. "She does not realize 'Boo to eating meat!'").
However, if ethical statements do not represent cognitions, it seems odd to use them as premises in an argument, and even odder to assume they follow the same rules of syllogism as true propositions.
Many objections to non-cognitivism based on the linguistic characteristics of what purport to be moral judgments were originally raised by Peter Glassen in "The Cognitivity of Moral Judgments", published in Mind in January 1959, and in Glassen's follow-up article in the January 1963 issue of the same journal.