Alasdair MacIntyre, answered from the texts and cited to the page.
Modern moral discourse is in a state of catastrophic disorder. We use moral language fluently — duty, obligation, rights, justice, virtue — but the conceptual scheme that gave the language its sense has been destroyed and what remains are fragments. The fragments are deployed in arguments that cannot reach rational conclusion because the disputants no longer share a framework for what the terms mean.
Emotivism — the meta-ethical theory of Stevenson and Ayer — is a poor philosophical theory of what moral judgements are; but it is an accurate description of what they have become in the culture of modernity. To assert "this is good" or "this is right" is, in the emotivist culture, to express a preference and to invite agreement; the appearance of an objective standard is a mask, and the unmasking is what makes Nietzsche's diagnosis irresistible to anyone who attends honestly to the language we actually speak.12345
After Virtue: Nietzsche or Aristotle, Trotsky and St. Benedict In Chapter 9 I posed a stark question: Nietzsche or Aristotle? The argument which led to the posing of that question had two central premises. The first was that the language—and therefore also to some large degree the practice—of morality today is in a state of grave disorder.After Virtue - A Study in Moral Theory, pp. 271–272
Contemporary moral disagreements of a certain kind cannot be resolved, because no moral disagreements of that kind in any age, past, present or future, can be resolved. What you present as a contingent feature of our culture, standing in need of some special, perhaps historical explanation, is a necessary feature of all cultures which possess evaluative discourse.After Virtue - A Study in Moral Theory, pp. 27–28
How ought we to write the history of such changes? It is in trying to answer this question that the connection between these features of contemporary moral debate and my initial hypothesis becomes clear.After Virtue - A Study in Moral Theory, p. 27
That this is so throws light on the theory of moral utterance that immediately succeeded Prichard's intuitionism. Emotivism has always been an implausible theory about the meaning of moral words and sentences. "Good," "right," and "ought" involve an appeal to some standard which expressions of preference or choice or imperatival expressions do not involve; and as R. M.Against the Self-Images of the Age, p. 171
And how should we characterize their disagreements? It is here that we cannot do without a well-grounded philosophical account of what we are doing and saying when we assert "It is good to... " or "It is good that... " and other such cognate sentences.Ethics in the Conflicts of Modernity, p. 17
The foundational thesis of After Virtue. Defended through the rest of the corpus. Opposed by analytical moral philosophers who see modern moral discourse as functioning normally. Charged with nostalgia for false historical unanimity by Nussbaum (1989); charged with overstatement by Stout (2004). The thesis is not that moral language is meaningless but that its operations have been severed from the framework that gave them sense.