MacIntyre asks us to imagine a scenario in which scientific investigation is utterly abolished and all relevant scientific data destroyed. Next, a movement against this anti-science movement seeks to restore science, but only has fragments of the original data. They possess fragments of the original documents, but lack the context in which these original data made sense. Furthermore, since they lack the context in which these original documents made sense, they no longer have knoweldge of the use and function of the scientific instruments which remain.
Such a society made memorize the partial and fragmented data of these documents, but, lacking the context in which the data of the documents originally made sense, they cannot really be said to understand the data. Copying and pasting a segment from Newton's writing on absolute space and time with a piece of data from quantum mechanics, and combining it with a piece describing phlogiston theory, 21st century neuroscience, phrenology, and so on, and memorizing all the data, does not produce scientific knowledge. It produces incoherent nonsense. We may still use the terminology of the original documents, but we are not using the terms in the same way because we do not understand the context in which the terms alone had meaning.
MacIntyre argues that this is a description of our contemporary world with respect to ethics. We use moral and ethical terminology, but we abstract the terminology from the worldview in which these terms originally had meaning, and we are thus speaking nonsense, because we place this absolutist language in the highly relativistic context of the modern world. We use terms like "good" and "evil" or "wrong," but we are using it within a context and worldview which rejects the context of absolute standards according to which these terms originally had meaning.
We are basically what MacIntyre refers to as emotivists. When we say that something is evil or good, we are only expressing our personal distaste or preference. We are not making objective statements. Nonetheless, we are acting like we are making objective statements when we use such statements, and it is clear that we believe we are making objective statements based on the outrage we exhibit when we use them.
MacIntyre makes the point that there is admittedly a fundamental difference between our present state of anomic, moral disorder and the hypothetical scenario concerning scientific anomie he has painted. In the hypothetical example, those who were victims of the catastrophe realized that they had experienced such a catastrophe. In our present state, we are wholly ignorant of such a thing. Most people are totally unaware that there is such a problem. Even academic historians, MacIntyre notes, are totally unaware of this problem. They are unaware of it because they are themselves victims of it.
Look, for example, at the rhetoric of the political philosopher, or slightly more recently than that, the rhetoric of the neo-Marxist member of the Frankfurt School. Or step back a few decades, or maybe a century or a century and a half, and look at the rhetoric of the older Marxists and the anarchists. Even while problematizing the notion of absolute standards of value and truth, their primary motive in doing so was ironically to justify their own standards and impose these standards on others. They spoke quite openly and unflinchingly about breaches of justice, about oppression, about objective right and wrong, and so on. Yet it is clear that if they are to be consistent, their own standards of right and wrong are as relative and evanescent as the conservative standards which they are critiquing.
MacIntyre, Alasdair (1981). After Virtue. 1-7. London, UK, New York, NY. Bloomsbury Publishing, Plc.