In Consilience: The Unity of Knowledge (1998), Edward O. Wilson recognized that crucial for his unification of all knowledge was a biological account of ethics as rooted in evolved human nature. He rightly noted that in doing this, he was following in the tradition of naturalistic ethics that stretches from Aristotle to David Hume to Adam Smith and to Charles Darwin. He was also right to see this naturalistic tradition of ethics as being "empiricist" in contrast to the "transcendentalist" ethics of those thinkers like Immanuel Kant who look to a transcendent realm of moral freedom beyond the natural world of human inclinations and experience. Since I agree with Wilson about this, it always seems strange to me that so many evolutionary psychologists have rejected Wilson's reasoning in favor of a Kantian transcendentalist view of morality, even though this contradicts any evolutionary explanation of morality as grounded in evolved human nature, which makes their account of morality incoherent.
For example, a few months ago, I wrote about Carlton Patrick's article--"Evolution Is the Source, and the Undoing, of Natural Law"--in which he assumed that John Finnis was correct in his Kantian interpretation of natural law as based on some "supernatural or metaphysical explanations" that transcend human nature. Patrick then showed how evolutionary psychology explains that "when we talk about morality, we are not talking about a cosmic mandate but rather a set of species-wide psychological instincts that are a part of human nature." But in thus refuting Finnis's Kantian distortion of natural law, Patrick ignored the fact that the natural law as understood by people like Thomas Aquinas and John Locke is rooted in human biological nature in a way that can be confirmed by evolutionary moral psychology.
I have also pointed out how Patrick and his coauthor Debra Lieberman have supported a Kantian rationalist view of ethics as transcending human biological nature, which denies the naturalist view of ethics defended by Locke, Darwin, and Westermarck.
Peter DeScioli is another example of an evolutionary psychologist who accepts Kant's transcendentalist morality, while still developing an evolutionary account of morality that contradicts that Kantian transcendentalism (DeScioli 2016; DeScioli and Kurzban 2009, 2013, 2018; Kurzban, DeScioli, and Fein 2012). DeScioli repeatedly refers to Kant's Groundwork for the Metaphysics of Morals as showing how moral judgment must depend on the "categorical imperatives" of a transcendental morality (see, for example, DeScioli and Kurzban 2013, 479-480; and Kurzban et al. 2012). He also endorses George Jackson Mivart's Kantian critique of Darwin's evolutionary moral psychology in The Descent of Man (DeScioli and Kurzban 2013, 479; Mivart 1893, 1973). Mivart insisted on a Kantian separation between nature and morality. Although the human body could be explained as a natural product of biological evolution, Mivart contended, the human soul was a supernatural product of divine creation. And as an expression of the soul's transcendence of nature, human morality manifested a uniquely human freedom from natural causality.
In the Groundwork, Kant posits a radical dualism that separates reality into two metaphysical realms. Judging what is the case belongs to the "phenomenal" realm of nature, but judging what ought to be belongs to the "noumenal" realm of freedom (Kant 1959, 3-5, 30, 44-45, 67-74, 80 [Academie edition, 387-89, 413, 426-28, 448-56, 460-62]). The distinction in English between is and ought corresponds to Kant's distinction in German between sein and sollen. For Kant, the natural world is governed by causal laws that can be understood by natural science; and in this world there can be no free will, because every event must be determined by a causal mechanism. By contrast, in our moral experience, we praise and blame people in accordance with a moral law that transcends nature and is thus unknowable by natural science; and in this moral world we must assume free will, because moral judgment would be impossible unless we assumed that people were capable of freely choosing to obey or disobey the moral law. As moral agents, we obey categorical imperatives of what ought to be, but this ought expresses a moral necessity that has no place in nature. "When we have the course of nature alone in view, ought has no meaning whatsoever" (Kant 1965, 473). As moral agents, human beings transcend the empirical realm of nature and enter a transcendent realm of freedom that belongs to them as rational beings not governed by the laws of nature.
Kant's separation of is and ought treats morality as an autonomous realm of experience governed by its own internal logic with no reference to anything in human nature such as natural desires and inclinations and the natural pursuit of happiness. The human pursuit of happiness is not truly moral because it is governed by the empirical hypothetical imperatives of prudence--if you desire to be happy, then you must cultivate the moral and intellectual virtues--but not by the categorical imperatives of pure moral reason--you must obey the moral law without regard to your natural desires for happiness.
This puts Kant in opposition to the ethical naturalists like Aristotle, Aquinas, Locke, and Hume, who say that the human good is the desirable, that human morality is the pursuit of happiness, and that the natural moral law corresponds to the order of the natural desires of human nature.
When Darwin developed his evolutionary theory of morality, he adopted the ethical naturalist position rather than a Kantian dualism. When he began his account of the moral sense in The Descent of Man, he quoted a passage from Kant's Critique of Practical Reason about how the word ought is one of the noblest traits of human beings. But in the immediately following passage of Kant's book, Kant said this experience of the moral ought shows us "man as belonging to two worlds" (Kant 1956, 90). Darwin, however, denied this Kantian dualism by indicating that he would approach morality "exclusively from the side of natural history," and he identified the power of the word ought as expressing instinctive moral emotion--"the deep feeling of right or duty" (2004, 120-21, 134, 136, 140, 147, 680).
DeScioli says that his evolutionary theory of morality is on the side of Kant rather than Darwin, because he accepts Kant's claim "that morality consists of 'categorical imperatives,' a set of actions that are morally wrong regardless of the goals these actions are intended to achieve," and DeScioli believes that laboratory research "has found that people often show Kantian moral thinking, focusing on specific actions rather than expected consequences" (DeScioli and Kurzban 2013, 479).
DeScioli claims that the Kantian morality of categorical imperatives is shown clearly in how most people think about the Trolley Dilemma. Imagine that you see a runaway trolley speeding down a track, and five people who have somehow become bound to the track will be killed. You see that there is a switch that will turn the trolley onto a sidetrack and save the lives of the five people. Unfortunately, however, there is one person bound to the sidetrack who will be killed if you throw the switch. Should you throw the switch--killing one person but saving five?
Now imagine that you are on a footbridge over the tracks. You see the runaway trolley and the five people who will be killed if the trolley is not stopped. There is no switch to divert the trolley onto a sidetrack. You could jump onto the track and try to stop it. But let's say that you are such a small person that you're unlikely to stop it. You notice, however, that there is a fat man standing near you, and if you push him onto the tracks, he will probably stop the trolley, but he will be killed. Should you push the fat man--killing one person but saving five?
Oh sure, as I have indicated in my previous posts on the Trolley Dilemma, this looks like a silly cartoon. But it does illustrate the kind of dilemma that some people have faced (perhaps in war), where killing one or a few people might save the lives of many.
When people are asked about these two trolley scenarios, most will say that they would pull the switch but would not push the fat man. This might seem strange since most are willing to kill one person to save five in the switch case but not in the footbridge case. What's the difference between the two cases?
(Actually, in one realistic simulation of the switch case, 5 of 7 individuals froze in fear and refused to throw the switch.)
As DeScioli indicates, the most plausible explanation has been offered by John Mikhail (2011), who says that what we see here is an intuitive moral understanding of the Principle of Double Effect. Thomas Aquinas stated this principle as part of his natural law jurisprudence. To reconcile the prohibition of intentional killing with the right to kill in self-defense, Aquinas explained: "Nothing prevents one action having two effects, only one of which is intended, and the other of which is unintended. . . . Therefore, one's action in defending oneself can have two effects: saving one's life and slaying the aggressor. And so such acts of self-defense, as one intends by them to preserve one's life, do not have the character of being unlawful, since it is natural for everything to keep itself in existence as far as possible" (Summa Theologica, II-II, q. 64, a. 7). Mikhail sees a general principle here: "the principle holds that an otherwise prohibited action, such as battery or homicide, which has both good and bad effects may be permissible if the prohibited act itself is not directly intended, the good but not the bad effects are directly intended, the good effects outweigh the bad effects, and no morally preferable alternative is available" (Mikhail 2011, 148-49).
Mikhail applies this Principle of Double Effect to explain how most people distinguish the switch case from the footbridge case in the Trolley Dilemma. If there is no morally preferable alternative, most people would pull the switch to intentionally save the five lives, while foreseeing but not directly intending the death of the one person on the sidetrack. We know that the killing is not intended, because if the person on the sidetrack could escape and save his life, the bystander who pulled the switch would be pleased with this outcome. By contrast, to push the fat man off the footbridge would be a directly intended killing; and we know that because if the fat man could run off the track to save his life, the intended outcome of the bystander who pushed him would not be achieved.
Mikhail sees this Principle of Double Effect as one manifestation of an "intuitive jurisprudence" rooted in "a common moral nature" and "a common sociobiological instinct" that illustrates the naturally evolved moral sense identified by Darwin in The Descent of Man (Mikhail 2011, 57, 148, 172; Darwin 2004, 132-38).
I don't see how this conforms to Kant's metaphysical morality. Kant never speaks about the Principle of Double Effect. And he clearly denies that moral judgment can be rooted in any instinctive moral sense of human nature, because pure moral reasoning belongs to a noumenal realm of pure moral reason that transcends the empirical reality of nature.
And yet, DeScioli insists that how people judge the trolley dilemma manifests the categorical imperatives of Kantian morality. "Immanuel Kant would argue . . . that when humans face this dilemma, they should not kill one to save five because there is an inviolable moral rule against killing that cannot be broken regardless of the consequences" (Kurzban, DeScioli, and Fein 2012, 323). In the footbridge version of the trolley dilemma, most people do seem to judge that in that situation, it is wrong to kill one person to save five people. But in the switch version, most people judge that in that situation, it is right to kill one person to save five. And so they do not believe in a Kantian categorical imperative that "there is an inviolable moral rule against killing" in all situations, as DeScioli asserts. Rather, they believe that the rightness or wrongness of killing depends upon the situation. So that in a situation where one must kill one person to save five people, and that killing is not directly intended, that killing is not wrong. But in a situation where one directly intends to kill one person to save five people, that killing is wrong.
Similarly, in a situation where killing an attacker is the only way to save one's life, that killing in self-defense is not wrong, because one is not directly intending the killing, as indicated by the fact that if the attacker were to retreat or surrender, one would not kill him. A comparable moral principle of the law of just war is that combatants must not directly intend to target innocent people for attack, although innocent people might die as an unintended side-effect of directly attacking military targets. Combatants may attack and kill enemy combatants who threaten them, but if those enemy combatants surrender, then they may not be killed.
Here we see that Kant's categorical imperative (never kill) fails, because it does not allow for prudence in recognizing the variability in our moral judgments of right and wrong as applied to variable situations.
In a recent article in Evolution and Human Behavior, DeScioli seems to pull away from his earlier attempts to ground an evolutionary theory of morality and law in Kantian moral philosophy (De Scioli 2023). He says nothing about Kant. He argues that moral rules and laws evolved as a strategy for choosing sides in conflicts by impartial rules of action. And this would seem to be grounded not in Kant's categorical imperatives but in the hypothetical imperatives of Thomistic and Lockean natural law as rooted in evolved human nature. I will comment on that article in my next post.
Darwin, Charles. 2004. The Descent of Man. Penguin Classics.
DeScioli, Peter. 2016. "The Side-Taking Hypothesis for Moral Judgment." Current Opinion in Psychology 7:23-27.
DeScioli, Peter. 2023. "On the Origin of Laws by Natural Selection." Evolution and Human Behavior 44: 195-209.
DeScioli, Peter, and Robert Kurzban. 2009. "Mysteries of Morality." Cognition 112: 281-99.
DeScioli, Peter, and Robert Kurzban. 2013. "A Solution to the Mysteries of Morality." Psychological Bulletin 139: 477-496.
DeScioli, Peter, and Robert Kurzan. 2018. "Morality Is for Choosing Sides." In K. Gray and J. Graham, eds., Atlas of Moral Psychology, 177-185. New York: Guildford Press.
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Kurzban, Robert, Peter DeScioli, and Daniel Fein. 2012. "Hamilton vs. Kant: Pitting Adaptations for Altruism Against Adaptations for Moral Judgment." Evolution and Human Nature 33: 323-333.
Mikhail, John. 2011. Elements of Moral Cognition: Rawls' Linguistic Analogy and the Cognitive Science of Moral and Legal Judgment. New York: Cambridge University Press.
Mivart, St. George Jackson. 1893. "Evolution in Professor Huxley." The Popular Science Monthly 44: 319-33.
Mivart, St. George Jackson. 1973. "Darwin's Descent of Man." In David Hull, ed., Darwin and His Critics, 354-84. Chicago: University of Chicago Press.
Patrick, Carlton. 2023. "Evolution Is the Source, and the Undoing, of Natural Law." Evolution and Human Behavior 44: 175-183.
Wilson, Edward O. 1998. Consilience: The Unity of Knowledge. New York: Knopf.