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It’s Revolting!


The contrast in literary and intellectual style between these two books on the same subject, both by philosophers, could hardly be greater. Here is a typical passage from Daniel Kelly:

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Binnie Hale and George Grossmith Jr. in No, No, Nanette, circa 1925
Taken together, the emotion of disgust consisted of a rigid, reliable type of motivation and behavior, paired with an open-ended database of elicitors and a flexible acquisition system, enhanced with a sentimental signaling system available for the transmission of cultural information. As new adaptive problems arose, these features, and the mix of rigidity and flexibility they offered, made the disgust system well positioned to be co-opted to new purposes, including purposes that had little or nothing to do with food intake or disease avoidance.
When considered next to each other, (a) the conditions created by the core coevolutionary feedback loop and (b) the nature of the disgust system seem an almost ideal match for each other: the feedback loop generates a variety of new adaptive problems, involving especially social interactions, and the disgust system lends itself to being co-opted to deal with new adaptive problems, especially those involving social interactions.

And here is a typical passage from Colin McGinn:

In the rotting corpse, we see something that once housed a conscious being and no longer does—and it is as if the consciousness still obscurely resides within the body awaiting its final dissolution. The consciously living is still somehow hovering around the organically dead, and the dead impinges on the living: this is a moment of deep metaphysical transition—consciousness turning to mindless, disorganized matter.
Similarly, in feces we can see the death of living things, some of them sentient, which have ended up as food; but as well, we see the life processes of a sentient being at work. The conscious life of the food animal is obscurely present in the feces of the predator—after all, it has been consumed along with the organic tissue—but we can also see the imprint of the conscious life that has done the consuming. Conscious animal digests conscious animal: shit is the visible sign of absorption. The strange vitality of shit, phenomenologically speaking, reflects its embedding in the world of sentience.

Both books address an absorbing and difficult question—the nature, meaning, and value of disgust—that in recent years has generated a large psychological literature. Unlike fear and anger, but like shame and guilt, disgust seems to be an emotion unique to humans, and like language it appears only at a certain stage of human development. It has a great range of objects, and those objects can differ widely among persons and cultures, and over time, though there seem to be some that are universal, such as rotting corpses, suppurating wounds, snot, pus, vomit, excrement, and menstrual blood. Among the objects that vary are species of animal—rats, worms, cockroaches—sexual practices, foods, ethnic groups, and perhaps some moral offenses. Some benighted souls find French delicacies like tête de veau and the riper cheeses revolting. We have witnessed a big cultural shift not just in common opinion but in common visceral feelings about homosexuality and sexual variety in general. And disgust at interracial contact has lessened dramatically with the weakening of the caste systems that it supports.

Some of the objects of disgust are harmful, but most are not. What, if anything, do they have in common? Or rather, what is the common repellent quality that the emotion of disgust senses in them all, that makes us shrink so desperately from contact with the disgusting? Fire is dangerous but not disgusting; vomit is disgusting but not dangerous. What is it that we see in the second but not the first?

Kelly and McGinn give very different answers to these questions, and address them with very different methods. Kelly offers functionalist psychological models that explain observable behavior, buttressed by the sort of evolutionary speculation that one now encounters in practically all spheres of thought. McGinn’s approach is phenomenological, an attempt to understand the experience and conceptual meaning of disgust from within, though he too engages in some freewheeling evolutionary speculation. Kelly mostly leaves aside the first-person phenomenology of disgust, because it doesn’t fit into his explanatory project; McGinn leaves aside moral disgust and the role of disgust in policing the boundaries of social groups. So there is a sense in which these two studies are complementary. Nevertheless, their results are in important ways incompatible: McGinn finds in the diversity of disgust a unity that Kelly’s account denies.


Kelly’s functionalist approach, presented with the aid of dispiriting box charts depicting the organization and operation of the human mind, identifies each type of mental state as part of an interlocking system whose workings provide the causal link between observable inputs and observable outputs for a living organism. This system is assumed to depend at a more basic level on the organization and operation of the brain, and Kelly occasionally refers to data from neuroscience, but he is essentially engaged in behavioral science.

His theory combines three elements, which he calls the Entanglement Thesis, the Cultural Transmission Model, and the Co-opt Thesis. According to the Entanglement Thesis, two primitive protective responses combined at some point in human evolution to form a single emotion:

One mechanism…evolved as an adaptive response to the ingestion of toxins and harmful substances. The other…evolved as an adaptive response to the presence of disease and parasites in the broader physical and social environment.

That is why the typical manifestation of disgust, whatever the object, includes not only nausea and movements of the mouth as if to expel something noxious, but also horror of all contact with the object and the sense that it will contaminate anything else with which it comes into contact. The entanglement resulted from the expansion of the human diet to include meat, after the invention of tools, which rendered humans more vulnerable to infection. The resulting emotion was naturally associated with eating and sex, both of which are necessary but potentially dangerous; and it took on the role of monitoring the boundaries of the body and the bodily orifices, which are avenues for possible infection.

According to the Cultural Transmission Model, the disgust response also served to warn others of dangers of poisoning and infection—information whose dissemination in a gregarious species is advantageous for everyone, since we can all infect one another. Finally, according to the Co-opt Thesis, once humans began to form groups governed by social norms, the already existing disgust response attached itself to conventional dietary and behavioral restrictions that helped define the boundaries between groups and regulated certain aspects of social and personal life. Purity norms (such as the rule never to touch food with the left hand, which is reserved for body maintenance) and taboos restricting sexual partners and conduct seem to be enforced by disgust in all societies. These are examples of Gene-Culture Coevolution: a biologically based mechanism acquires new functions in cultural systems that it helps to sustain.

Another important example is the role of disgust in the enforcement of ethnic, racial, or caste boundaries. Disgust ensures that contact with outsiders is felt to be contaminating, and the characteristics or practices that distinguish outsiders from members of one’s own group are seen as impure and repellent. Tribal solidarity facilitates useful in-group cooperation, but it is dangerous to interact with those who give no evidence of membership in one’s own community with its shared norms. Hence, as Kelly says, “certain forms of ethnocentrism, though often repugnant and largely at odds with moral codes founded on equality and egalitarianism, could very well be adaptive.”

Finally, Kelly argues that if we accept his account of how disgust has been co-opted to enforce taboos and moral norms, we should accord it no independent authority as a form of insight into what is really bad or wrong:

I am claiming that, while reflecting on and carefully deliberating about the moral status of a norm, activity, practice, or ideal, the moral significance that should be assigned to the fact that people are disgusted by it is: none.1

The fact that we find an object, or a person, or a social or sexual practice disgusting gives us absolutely no reason to judge it objectionable. Any such judgment must be based on more objective features.

Kelly’s conclusion is that, while in its biological origins disgust had a fairly well-defined set of objects, it has since been attached to such a variety of cultural norms that it now lacks a single coherent meaning. Not only is there nothing all disgusting things have in common, but there is nothing that we take them to have in common in finding them disgusting.


McGinn is interested not only in the causes and effects of disgust. He wants to describe it from the inside, especially its cognitive content, the beliefs or attitudes embedded in it. Disgust is an emotion, and emotions are not mere sensations: they are permeated with thought. McGinn’s aim is to discover what in the content of disgust corresponds to the sense of danger in the content of fear. Clearly belief is involved in triggering disgust. If you feel something soft and slippery, it will make a difference whether you think it is a litchi nut or a detached eyeball. But what does the difference consist in?

McGinn starts by cataloging the things that most humans find disgusting, and he really lets himself go. We are above all disgusting ourselves, inside and out. Bodily secretions, pimples, warts, wrinkled and aging flesh, dandruff, athlete’s foot, too much hair in the wrong places; and our internal organs are disgusting, including the moist, pulpy brain, but above all the alimentary canal, coiling like an immense worm from mouth to anus, filled with revolting gunk and producing inexhaustible quantities of stinking shit. A phenomenological investigation that aims to discover human universals runs the risk that others may not share the feelings of the investigator. For example, McGinn is eloquent in describing the sexual organs as disgusting (the penis like a suppurating tumor, the vagina like a bleeding wound), and he suggests that overcoming that disgust is part of sexual pleasure. This doesn’t resonate with me, since I don’t share that disgust reaction—though I would say that good sex dismantles the personal boundaries of civilization and it doesn’t hurt to have a dirty mind. (See Henry Miller.) But it would be rash to claim universality for any feature of sexual experience.

Creditably, McGinn does not describe the “elicitors of disgust” with clinical detachment, but does his best to express the feeling vividly enough to evoke it in the reader, so that we can confirm his phenomenological analysis from our own experience. He also stresses our ambivalence: we are drawn to the disgusting as well as repelled by it. And he notes two exceptions: the weakness or absence of disgust reactions to our own waste products, and the tolerance developed by medical personnel through habituation. McGinn conjectures that nurses, orderlies, and physicians merely suppress the behavioral signs of disgust, but not the emotion itself. Anecdotal evidence suggests to me, however, that those who can’t shake the emotion leave the profession or choose specialties like psychiatry or radiology that don’t require contact with the disgusting.

  1. 1

    Martha Nussbaum reaches the same conclusion in Hiding from Humanity: Disgust, Shame, and the Law (Princeton University Press, 2004), though her reasons are different. 

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