In the brief first chapter, MacIntyre proposes a thought experiment. He asks the reader to imagine a scenario in which the natural sciences were forgotten following a catastrophe. Human beings would be able to reassemble some of the ideas and concepts, but they would lack the necessary context to fully understand them. MacIntyre argues that this is exactly the state of “grave disorder” society is in when it comes to moral discussion. This is because we have largely “lost our comprehension, both theoretical and practical, of morality” (2). MacIntyre proposes to trace the historical causes for this loss in the book.

MacIntyre introduces his thesis that “emotivism” is the operative context in which modern moral debate takes place. The fact that moral discussion proceeds on the basis of emotion instead of reason means that disagreements are “interminable,” never able to reach a consensus. MacIntyre presents three representative contemporary moral arguments involving war, abortion, and the government’s role in the administering of health care and education.

The key feature of these debates is the “conceptual incommensurability” of the way they are framed. Both sides of a debate express a logically-coherent argument, yet the premises employ different “normative or evaluative concept[s]” (8), so that there is no way to weigh the competing claims.