I have defended an evolutionary theory of morality as rooted in the moral emotions of evolved human nature. In stressing the importance of the moral sentiments for moral psychology, this evolutionary theory belongs to the philosophic tradition of sentimentalist ethics that includes David Hume, Adam Smith, Edward Westermarck, Edward Wilson, and Frans de Waal--a tradition that is set against the Platonic and Kantian tradition of rationalist ethics.
I have written previously about how de Waal's version of this evolutionary theory recognizes both the continuity and discontinuity in the moral psychology of animals (de Waal 2006). According to de Waal, the moral sentiments constitute the first level of morality--the emotional building blocks of morality that include empathy, reciprocity, retribution, a sense of fairness, and reconciliation to resolve conflicts and restore harmonious relationships. These moral sentiments can be seen in some form in many species of nonhuman animals.
De Waal identifies social pressure as the second level of morality. Through social praise and blame, individuals are habituated to conform to the social rules of their group that maintain the good order of the community. These rules are enforced through reward, punishment, and reputation. In these ways, morality serves as a social contract for a cooperative society. Some of this can be seen in some nonhuman animals. For example, high-ranking males in chimpanzee groups engage in "policing behavior"--these males break up fights among others, and their intervention seems to be remarkably evenhanded. Nevertheless, the human morality of social pressure goes beyond the morality of other animals in that human beings can formulate social rules that are more abstract and systematic than is the case for other animals. Much of this abstract rulemaking depends on the human capacity for language.
Finally, judgment and reasoning constitute a third level of morality, and this is uniquely human. De Waal observes: "I know of no parallels in animals for moral reasoning" (2006, 174). We are like other social animals in that we care about our reputations--how we appear in the eyes of others--so that we want to be praised and not blamed by others. But we can also use our distinctly human capacity for abstraction and imagination to see ourselves mirrored in the eyes of an imagined "impartial spectator" (as Adam Smith called it), so that we want to do what is praiseworthy, regardless of whether we are actually praised by anyone. We care not only about our real reputation but also about our imaginary reputation. From this we develop an internal sense of self-esteem or conscience, so that even when other people do not punish us for our bad conduct, we punish ourselves by feeling guilt or shame. Those few human beings who never feel guilt or shame are psychopaths who have no conscience because they do not feel the moral emotions. (I have written about psychopaths as "moral strangers.") There is no evidence for anything like conscience or the impartial spectator in nonhuman animals. (I have written about Smith's concept of the "impartial spectator.")
And yet even if nonhuman animals do not show the full range of human morality, these animals do show some of the moral emotions; and therefore, de Waal argues, these nonhuman animals do deserve to be treated with some moral respect. But then we might wonder whether these animals have equal rights. Are we morally obligated to give equal consideration to the interests of all sentient beings, as Peter Singer has argued? Must we see the immorality not only in racism and sexism but also speciesism?
Recently, de Waal and Kristin Andrews have surveyed the evidence from affective neuroscience suggesting that many animals, even invertebrates, experience emotions of pleasure and pain that should give them some moral standing (de Waal and Andrews 2022). Through emotions and felt experience (sentience), organisms judge experiences as attractive or aversive, and these physical and mental states of attraction or aversion prepare the organism for adaptive action.
So, for example, since there is increasing evidence that lobsters are sentient and experience emotions of pleasure and pain, de Waal claims, it is wrong for human beings to kill them by boiling them. Either we shouldn't kill them at all, or there should find some ethical way to kill them.
But then de Waal recognizes that Singer's argument for equal animal rights fails because it's morally impossible for human beings to give equal consideration to the interests of all sentient beings. This is impossible because there is an evolved natural desire for in-group loyalty. This belongs to my list of the twenty natural desires.
There is an expanding circle of human moral concern that begins with each individual being concerned for himself and then extends first to the individual's family and friends and beyond that to the community, tribe, or nation, and beyond that to some humanitarian feeling for distant strangers who might be brought to one's attention, and then finally to all life forms. But typically, the moral emotions of sympathy become weaker as they are extended farther out on the expanding circle (de Waal 2006, 163-66).
Loyalty is a moral duty in that we expect people to care more for those close to them than to distant strangers or to nonhuman animals. Inevitably, there are conflicts of interest within and between species. So that moral systems are inherently biased towards the in-group. For that reason, the moral sentimentalists like Adam Smith, Edward Westermarck, and de Waal, who speak of the impartiality required for moral sentiments recognize that this cannot be an absolute impartiality but only an apparent impartiality. After all, if human beings were absolutely impartial, they would not care for themselves, for other human beings, or for other animals, because nothing would really matter.
That we should feel some sympathy for other animals, particularly for those animals that are close to us or that elicit our parental care, is an expression of our morality. We know that one sign that a child might grow up to be a psychopath is that he is unusually cruel in his treatment of animals. And it is mostly a he, because most psychopaths are male.
But still most of us agree that it is right to kill animals for food and other products, and that it is right to use animals for painful medical experiments necessary for developing drugs and therapies for human beings and for the scientific understanding of mammalian physiology and neurology. We should feel some concern for minimizing animal suffering. But we feel much more concern for minimizing human suffering.
As Westermarck observed, "absolute impartiality . . . would concede to all sentient creatures equal rights," but "impartiality . . . is not absolute, only relative, that is, impartiality within certain limits" (1900, 185). Our sympathy for nonhuman animals is limited by our partiality for human beings. "Humanity to animals" does require "that we ought to pay some regard to their feelings," Westermarck suggested, but this does not mean "that they should be regarded equally with the feelings of men" (1932, 213).
Even our sympathy for other human beings is limited by our in-group loyalty. In war, fighting for one's country against the enemy is a moral duty. Betraying one's country is treason. But still, it can be a moral duty to refuse to fight in an unjust war.
de Waal, Frans. 2006. Primates and Philosophers: How Morality Evolved, edited by Stephen Macedo and Josiah Ober. Princeton, NJ: Princeton University Press.
de Waal, Frans, and Kristin Andrews. 2022. "The Question of Animal Emotions." Science 375: 1351-52.
Westermarck, Edward. 1900. "Remarks on the Predicates of Moral Judgment." Mind 9: 184-204.
Westermarck, Edward. 1932. Ethical Relativity. London: Kegan Paul, Trench, Trubner and Company.