MacIntyre holds that After Virtue makes seven central claims. It begins with an allegory suggestive of the premise of the science-fiction novel A Canticle for Leibowitz: a world where all sciences have been dismantled quickly and completely. MacIntyre asks what the sciences would look like if they were re-assembled from the remnants of scientific knowledge that survived the catastrophe. He claims that the new sciences, though superficially similar to the old, would in fact be devoid of real scientific content, because the key suppositions and attitudes would not be present. "The hypothesis which I wish to advance," he continues, "is that in the actual world which we inhabit the language of morality is in the same state of grave disorder as the language of natural science in the imaginary world which I described." Specifically, MacIntyre applies this hypothesis to advance the notion that the moral structures that emerged from the Enlightenment were philosophically doomed from the start because they were formed using the aforementioned incoherent language of morality. MacIntyre claims that this failure encompasses the work of many significant Enlightenment and post-Enlightenment moral philosophers, including Kierkegaard, Marx, Kant, and Hume. These philosophers "fail because of certain shared characteristics deriving from their highly specific historical background.":51 That background is the Enlightenment's abandonment of Aristotelianism, and in particular the Aristotelian concept of teleology. Ancient and medieval ethics, argues MacIntyre, relied wholly on the teleological idea that human life had a proper end or character, and that human beings could not reach this natural end without preparation. Renaissance science rejected Aristotle's teleological physics as an incorrect and unnecessary account, which led Renaissance philosophy to make a similar rejection in the realm of ethics. But shorn of teleology, ethics as a body of knowledge was expurgated of its central content, and only remained as, essentially, a vocabulary list with few definitions and no context. With such an incomplete framework on which to base their moral understanding, the philosophers of the Enlightenment and their successors were doomed from the beginning.
MacIntyre illustrates this point through an example of a people who, he argues, experienced a similar incoherence in their own moral and ethical tradition: the Polynesian people of the South Pacific and their taboos. King Kamehameha II removed the taboos of the people in order to modernize their society and met little if any resistance. The Polynesians had no issue with abandoning their long-standing cultural traditions and MacIntyre claims this is because the taboos, though once meaningful to the islanders, had been shorn over the centuries of their underlying spiritual and didactic purpose, becoming a set of arbitrary prohibitions. The fact that Kamehameha II could abolish them so easily and without opposition is evidence, MacIntyre argues, of their incoherence. A similar incoherence, he argues, bedevils the ethical project since the Enlightenment.
Another reason MacIntyre gives for the doomed nature of the Enlightenment is the fact that it ascribed moral agency to the individual. He claims this made morality no more than one man's opinion and, thus, philosophy became a forum of inexplicably subjective rules and principles. The failure of the Enlightenment Project, because of the abandonment of a teleological structure, is shown by the inadequacy of moral emotivism, which MacIntyre believes accurately reflects the state of modern morality.
MacIntyre offers a strong critique of Friedrich Nietzsche, whom he calls the "King Kamehameha II of the European tradition," in reference to the Polynesian allegory above.:113 MacIntyre explains that, "Nietzschean man, the Übermensch, [is] the man who transcends, finds his good nowhere in the social world to date, but only that in himself which dictates his own new law and his own new table of the virtues.":257 Although he disagreed with Nietzsche's inegalitarian and elitist view of humankind, he acknowledged the validity of Nietzsche's critique of Enlightenment morality as an explanation of the latter's degeneration into emotivism, and that, like Kamehameha II, Nietzsche had identified the moral imperatives of his time as arbitrary and incoherent in demanding their abolition. The nineteenth-century critic who has most lastingly and profoundly influenced MacIntyre is not Nietzsche but Marx — indeed, After Virtue originates in MacIntyre's plans to write a book repairing the moral weaknesses of Marxism.:ix-x His critique of capitalism, and its associated liberal ideology and bureaucratic state (including what, in After Virtue, he condemned as the state capitalism of the USSR) is not expressed in traditional Marxist terms. Instead, it is written as a defence of ordinary social 'practices', and of the 'goods internal to practices'. Pursuit of these helps to give narrative structure and intelligibility to our lives, but these goods must be defended against their corruption by 'institutions', which pursue such 'external goods' as money, power and status (chapters 14-15).
MacIntyre seeks to find an alternative to Nietzsche's philosophy and eventually concludes that only classic Aristotelian thought can hope to save Western humanity. While Nietzsche seems to include the Aristotelian ethics and politics in his attack on the "degenerate disguises of the will to power,":127 MacIntyre claims that this cannot be done due to important differences between the structure and assumptions of Aristotelian and post-Enlightenment philosophy. These include:
- Aristotle's assumption that man is as-he-happens-to-be and that this is distinct from man-as-he-should-be. The Enlightenment, on the other hand, offers no metaphysical framework whatsoever in place of teleology.
- Aristotle's claim that rules are based on virtues, which are derived from an understanding of the telos. The Enlightenment reversed this and predicated virtues on an understanding of subjective (but purported to be universal) principles.
- Aristotle's assertion that virtue and morality are integral parts of society, as an understanding of the telos must be social and not individual. In the Enlightenment, however, societies lost their moral authority and the individual became the fundamental interpreter of moral questions.
MacIntyre opposes Nietzsche's return to the aristocratic ethics of Homeric Greece with the teleological approach to ethics pioneered by Aristotle. Nietzsche’s critique of Enlightenment moral theory does not work against a teleological ethics. For MacIntyre, "Nietzsche replaces the fictions of the Enlightenment individualism, of which he is so contemptuous, with a set of individualist fictions of his own.":129 Nietzsche’s übermensch, his solution to the lies of the Enlightenment, exposes the failure of the Enlightenment's epistemological project and of its search for a subjective yet universal morality. Nietzsche neglects the role of society in the formation and understanding of tradition and morality, and "Nietzsche’s great man cannot enter into relationships meditated by appeal to shared standards or virtues or goods; he is his own only moral authority and his relationships to others have to be exercises of that authority... it will be to condemn oneself to that moral solipsism which constitutes Nietzschean greatness.":258
After Virtue ends by posing the question 'Nietzsche or Aristotle?', although MacIntyre acknowledges that the book does not give sufficient grounds for a definitive answer that it is Aristotle, not Nietzsche, who points to the best solution for the problems that the book has diagnosed. Those grounds are set out in MacIntyre's subsequent works, in which he elaborates a sophisticated revision of the philosophical tradition of Aristotelianism.
In the end, however, MacIntyre tells us that we are waiting not for Godot but for St Benedict. MacIntyre charges a strong critique against individualist political philosophy, such as John Rawls' A Theory of Justice and Robert Nozick's Anarchy, State, and Utopia. To MacIntyre, morals and virtues can only be comprehended through their relation to the community in which they come from. Whereas Rawls tells us to conceive of justice through abstracting ourselves from who we are (through the veil of ignorance, for example) MacIntyre disagrees. Running throughout 'After Virtue' is the belief that in order to comprehend who we are, we must understand where we come from.