A Canticle for Leibowitz
In the initial chapters of the book, MacIntyre draws a parallel between the current state of morality in modernity and the premise for Walter Miller's 1959 science fiction novel A Canticle for Leibowitz. In this novel, civilization has been nearly destroyed by an apocalyptic event, and due to a turn against scientists before its collapse, only fragments of scientific documents are left over. These fragments can be compiled into a sort of scientific system, but it's empty: the foundation is either forgotten or nonexistent. MacIntyre uses this scenario as a metaphor for the current state of morality: after the Enlightenment, the foundation of morality was lost, and the vestiges are all that's left.
Characters
"Both individuals and roles can, and do, like characters, embody moral beliefs, doctrines and theories, but each does so in its own way." (Chapter 3: Emotivism)
In this passage, MacIntyre is speaking of the powers of fiction. He argues that people and their roles can actually embody moral beliefs, as do characters in novels, which is a testament to their effectiveness in getting their philosophical point across: not only do they clearly elaborate their viewpoints, but their actions serve to emphasize and hammer in the message to the reader's mind.
A Nonsensical Check
"Lacking any such social form, the making of a claim to a right would be like presenting a check for payment in a social order that lacked the institution of money." (Chapter 6: Some Consequences of the Failure of the Enlightenment Project)
In this section, MacIntyre is explaining the non-universal character of the concept of specific human rights. Without a social framework, he argues, claiming a right wouldn't make any sense; as he says in this apt simile, it would be like presenting a document that ensured something that doesn't actually exist.
King Charles II's Dead Fish
"Yet perhaps explanations are not needed, for perhaps the failure that the dominant tradition tries to explain is like King Charles II's dead fish." (Chapter 8: The Character of Generalizations in Social Science and their Lack of Predictive Power)
This section is devoted to an investigation of social science, and why it seems to be failing - or, at least, not operating at optimal function. Perhaps, MacIntyre argues, this is trying to explain something that isn't actually true. The example he references is this simile is an entertaining and apropos one: King Charles II, according to the story, asked the members of the Royal Society (a prestigious organization of intellectuals in England) why a dead fish weighs more than a living fish. Various theories were offered before Charles revealed that the dead fish doesn't actually weigh more.
King Kamehameha II
To explain the lack of a moral foundation in modernity, along with the strong influence of Friedrich Nietzsche, MacIntyre uses an allegorical metaphor that incorporates a real-life event. He argues that the erosion of morality in modernity resulting from the Enlightenment is like the erosion of the meaning of the Polynesian taboo rules; when King Kamehameha II ruled to abolish them, no one protested because they had no grasp of their roots or ultimate meaning. Such is modernity, says MacIntyre: we don't have a frame of reference for morality since the foundational meaning has worn away long ago.
