A.J. Ayer, answered from the texts and cited to the page.
Ethical concepts are pseudo-concepts. The statement "stealing money is wrong" has the same factual content as the statement "stealing money" uttered with a tone of horror or accompanied by an exclamation mark; the value-component is the expression of an attitude of disapproval, not the description of an additional moral fact.1 Aesthetic statements work the same way.
The position is emotivism, sometimes caricatured as the boo/hoorah theory ("boo to murder! hooray for kindness!"), but the considered position is more sophisticated than the caricature: ethical and aesthetic statements have rule-governed and prescriptive features the cruder emotivism missed, and the refined position acknowledged in Philosophical Essays' 'On the Analysis of Moral Judgments' (1949) and the engagement with Hare's prescriptivism preserves the central insight while addressing the structural complaints.2
Moral disagreement is real disagreement of attitude rather than pseudo-disagreement; moral judgement has real practical importance; ethics is not reducible to mere preference. What the position rules out is moral cognitivism — the view that moral statements describe mind-independent moral facts — and the metaphysical commitments that cognitivism requires.3
Could not the disagreement about the rightness or wrongness of Brutus's action be held to consist rather in the expression of conflicting attitudes than in the assertion of incompatible statements? Just as in the example of the oysters, the bestowal on the action by the opposing parties of what appear to be incompatible predicates would be logically deceptive.Freedom and Morality, pp. 28–29
And 106 as we have already rejected the "naturalistic" theories which are commonly supposed to provide the only alternative to "absolutism" in ethics, we seem to have reached a difficult position. We shall meet the difficulty by showing that the correct treatment of ethical statements is afforded by a third theory, which is wholly compatible with our radical empiricism.Language, Truth and Logic, p. 106
Thus, in the present instance, it is no doubt correct to say that the moralist does make statements, and, what is more, statements of fact, statements of ethical fact. It is correct in the sense that if a vote were taken on the point, those who objected to this way of speaking would probably be in the minority.Philosophical Essays, p. 248
Emotivism in LTL Chapter 6 is one of the most-cited and most-criticized positions in twentieth-century moral philosophy. Stevenson's Ethics and Language (1944) developed the parallel American version; Hare's prescriptivism is the most sophisticated descendant. The cognitivist tradition (Foot, Anscombe, McDowell, Wiggins) has been the major opposition; Mackie's error theory is a different non-cognitivist alternative; Blackburn's quasi-realism is the contemporary descendant of the emotivist programme that preserves the surface grammar of moral discourse while refusing the cognitivist commitments. The Hahn-volume essays by Wiggins and Kivy are the major late-career engagements; Ayer's replies refine and defend the position.