In my report, I did state some disagreements with Mizzoni's arguments. My most fundamental disagreement was my denial of Mizzoni's claim that Kantian ethics was compatible with evolutionary science's account of human nature and human morality. I argued that the general conclusion emerging from evolutionary moral psychology is that the Humean sentimentalists are right, and the Kantian rationalists are wrong. This is clear, for example, in the studies of psychopaths that show that their moral poverty arises not from any deficiency in their capacity for rational judgment but from their lack of moral emotions. I also argued that in order to defend Kantian ethics, Mazzoni simply assumed, without any supporting argumentation, the truth of Kant's dualistic separation of is and ought as belonging to two worlds--the phenomenal and the noumenal, the realm of nature and the realm of freedom.
I elaborated these points in a post.
Mizzoni's book has now been published. The book shows some revisions in response to my suggestions and criticisms. He responds to my major criticisms in two passages. In the section of his book where he responds to "potential objections," he has added one of my objections. He writes:
"PO5. By premising my inquiry on the landscape of moral philosophy, I am making unwarranted assumptions. It might be objected that by assuming the distinction between is and ought, the distinction between metaethics and normative ethics, and separating biological inquiry from normative inquiry, I am assuming a Kantian ethic and a Kantian metaphysics. The objection implies that I have characterized all normative ethics as Kantian and thereby disallowed a Darwinian explanation of morality."
"I do not think that observing a gap between statements of fact (is) and statements of ethics (ought), or a distinction between metaethics and normative ethics, or separating biological inquiry from normative inquiry commits one to a Kantian ethics, much less a Kantian metaphysics."
". . . I take the is/ought dichotomy to be simply a logical distinction: Is-statements function differently than ought-statements. Likewise, the distinction between normative ethics and metaethics is a logical one. They are different types of inquiry that ask different questions. A normative ethical theory must answer the question: What should I do? A metaethical theory must answer the question: What is the status of ethics? Normative ethics offers practical guidance about what constitutes ethical conduct."
"So further, since we are agents, we must decide how to act, and we do this from a first-person perspective. Since metaethics engages with more general questions about the status and origins of ethics, it is a level of inquiry operating at more of a third-person perspective. Biological science, also, provides a third-person perspective, thus it can be distinguished from a normative first-person perspective ethics."
"These seem to me to be minimalist assumptions, not uniquely Kantian assumptions, so I do not think I am characterizing all normative ethics as Kantian ethics. Kant may observe these distinctions, and attempt to shore them up with an extravagant metaphysics, but a Kantian metaphysics is not required to draw these logical distinctions. As I have mentioned, all ethical theories have some kind of background metaphysical assumptions . . ., but those assumptions can usually be separated from the specifically ethical components. I think contemporary Kantian deontologists have done this, for example, and sought only to develop and defend the ethical components of Kantian deontology" (238-39).Mizzoni recognizes that there are many Darwinian critics of Kantian ethics--such as Edward Wilson, Richard Dawkins, Stephen Jay Gould, Joshua Greene, and Michael Ruse--who say that Kant's categorical imperative does not conform to the world of human experience as studied by biological science. But Mizzoni denies that this undermines Kantian ethics: "The fact that a normative ethical principle advises what ought to be done, as opposed to advising to continue what is done in the natural world is not thereby a mark against that normative principle. Normative principles are meant to do more than simply describe and align with the world as it is" (190).
Gould has defended an ethics of hypothetical imperatives--such as the Golden Rule as a principle based on enlightened self-interest--as being superior to a Kantian ethics of categorical imperatives. Mizzoni responds: "His point against Kantian deontological ethics is that it doesn't fit with a complex and sloppy world. Maybe so. But should it? Kant's point about ethics being about the realm of freedom is because ethics is meant to free us from the world around us" (187).
"The best case for supporting a Kantian ethic," Mizzoni observes, "is to emphasize it as a normative ethic, not as a description of how ordinary humans make moral judgments" (180). In a footnote to this sentence, he writes: "There may be some passages in Kant, where, caught up in enthusiasm, he may blur the distinction between offering an account of how humans ordinarily make moral judgments, and how humans should make moral judgments" (192).
Is Kant "caught up in enthusiasm" when he tries to believe that acting according to categorical imperatives--acting by pure reason without any motivation by emotion or desire--is possible? If ought implies can, then the idea of a categorical ought is indefensible in so far as it is impossible.
If the biological study of human nature shows that acting according to hypothetical imperatives is possible, but acting according to categorical imperatives is not, then hasn't biological science thus denied Kantian ethics?
Mizzoni briefly recognizes the contrast between hypothetical and categorical imperatives in only two passages (187, 192 n. 4). And he fails to see that the impossibility of acting according to categorical imperatives means that Kantian ethics is impossible, and therefore that the only possible form of ethics is an ethics of hypothetical imperatives that combine reason and desire. (I have written about the ethics of hypothetical imperatives in a previous post.)
I can agree that Kant was at least partly right in recognizing the importance of general principles in moral judgment--principles like the Golden Rule. The Humean and Smithian sentimentalists also recognize this: they have defended a natural morality of informed desire, in that the good is the desirable, and reason judges how best to satisfy the desires in the most harmonious way over a whole life. What Kant says about the universality of moral reasoning is close to what Smith says about the reasoning of the impartial spectator.
But Kant was mostly wrong in assuming that moral judgment ought to be based on pure reason without any motivation by desire or emotion. This cannot be correct because it's impossible.
In fact, Mizzoni implicitly concedes this when he speaks about the attempts by Mark Timmons and Michael Slote to save Kantian ethics by "joining a deontological normative ethics with an expressivist metaethic" to create a "sentimentalist deontology" (180-81). But Mizzoni does not recognize that this saves Kantian ethics by destroying it!
This same problem comes up in Mizzoni's response to my argument about the moral poverty of psychopaths:
"Research done on psychopaths reveals that they have no trouble carrying out abstract reasoning, yet they do show deficits in experiencing moral emotions. Some have taken this as a refutation of Kantian ethics, since if Kant's theory is correct, then supposedly one need not experience emotions to reach ethical conclusions, but only use one's reason in employing the categorical imperative. But this argument assumes t hat merely because a person has t he capacity to engage in abstract reasoning, then the person will generate defensible ethical conclusions. Why should we assume that? As mentioned above, Kant does recommend that we should strive to be idealized rational agents, but he does not assume that people are ideal rational agents. Also, are psychopaths familiar with the formal ethical principle that Kant calls the categorical imperative? And even people who are familiar with the principle can still use the principle poorly, such as the Nazi Adolph Eichmann who famously stated that he was familiar with Kant's principle and used it on a daily basis throughout his life (Arendt 1963)" (180).Mizzoni misses the point in my argument about how the moral poverty of psychopaths refutes Kant. If Kant were right in claiming that normative moral judgments must be based on pure reason without emotional motivation, then we would assume not that a psychopath "will generate defensible ethical conclusions," but that a psychopath "can generate defensible ethical conclusions." Unless Mizzoni shows us that it is possible for psychopaths to make defensible moral judgments and act on them, even though psychopaths do not feel moral sentiments, he has not refuted my argument for how the biological study of psychopaths denies Kantian ethics.