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.


After taking us on a tour of our slimy, putrescent underworld, he turns to the task of showing how it all makes sense. He acknowledges that disgust may have had the biological function of preventing the ingestion of toxic substances in the distant evolutionary past, but now it is something much more sophisticated. He will argue that it is a philosophical emotion.

His account builds on what others have said. In his descriptions of the experience and objects of disgust, he acknowledges a debt to the philosopher Aurel Kolnai.2 He also cites, as does Kelly, the work of Paul Rozin, the leading contemporary scientific investigator of the phenomenon, and in particular Rozin’s hypothesis that disgust expresses a horror of our animality and the fear of death.3 McGinn agrees with Rozin that it is no accident that humans are both the only animals to feel disgust and the only animals who know that they are going to die, but he argues that neither death nor animality provides the key to the emotion. Skeletons remind us of death, but are not disgusting. And most animals are not disgusting, nor are many of the features that we share with animals, like vision and locomotion.

The solution, according to McGinn, is that what disgusts us is death in the midst of life, the transition between them that appears, for example, in the rotting corpse, lately alive and now food for maggots and bacteria. He believes that this interpenetration of life and death is found in all the other instances of disgust, from sex to excrement. Further, he holds that the real source of this revulsion is our inability to escape the metaphysical tragedy of the dependence of our consciousness on the destructible human body:

The borderline of life and death is what produces disgust, according to the life-in-death theory, but this borderline is closely bound up with ideas of consciousness and its annihilation—as well as with the tragic and perplexing dependence of consciousness on biological matter. It is a kind of metaphysical emotion, spanning the divide between (roughly) mind and matter.

In a chapter called “Our Dual Nature,” McGinn observes that there is nothing about our conscious self as we experience it from the inside that suggests that it should be mortal. Conceived in this way we seem spiritual, transcendent, and godlike. Yet this higher existence turns out to depend on a lower one, the organic body:

To be more concrete: he who has a soul also has an anus—he who thinks also shits…. We are disgusting and we know it, know it in our marrow—yet we feel ourselves to be much more than that, and to exist essentially outside of it.

Finally, the biological inevitability of death because of our entanglement with the body seems to us gratuitous, “not dictated by the inner nature of the thing that dies, namely the conscious self.” Disgust is a form of rebellion against this perverse arrangement. That is why McGinn calls it a philosophical emotion.

There is a lot more, including a proposal that disgust may be an evolutionary corrective to humans’ unbridled lust, omnivorousness, and greed, preventing us from constantly eating and copulating with everything in sight, as we would have otherwise been inclined to do. This has no apparent connection with the death-in-life theory, but it overlaps with Kelly’s suggestion that disgust served the function of protecting humans from poisoning and infecting themselves once they moved beyond foraging as the source of food.


What is the status of the claims made by these two authors, and how can one decide whether they are true, or likely? Kelly’s claims are clearly causal and historical: they describe how the reaction of disgust formed and came to be attached to the objects that provoke it, by mechanisms of biological and cultural evolution. McGinn’s claims also have causal implications, but they are mainly of a special, interpretive kind, as is indicated by his title, The Meaning of Disgust.

I have no idea how to evaluate the historical claims. The Darwinian outlook that now prevails in our culture apparently licenses all teleological speculation about the function of a human practice or characteristic, on the assumption that it can be translated into an explanation by natural selection. It is supposed that chance variations in heritable psychological dispositions conferred selective advantage on their possessors, and once well established, these dispositions took on other functions through the same combination of chance and selective advantage. Kelly defends his hypothesis in comparison with some alternatives by claiming that it accounts for more of the currently observable features of disgust, and the variety of its elicitors. Perhaps that is the only evidence one can hope for, if one assumes the explanation must take an evolutionary form.

McGinn’s main claims are not historical; they are about what disgust is, what is really going on, psychologically, when we find something disgusting. These are claims about the experience, but not about its surface. He doesn’t mean that feces or worms evoke explicit thoughts of death or the metaphysics of mind and body. McGinn’s claim is more like a psychoanalytic interpretation—that these thoughts are behind the emotion. In Rozin’s view, the psychoanalytic form is explicit. He holds that at some level humans know that they are animals condemned to death, but this thought is unbearable and in order to repress it we have developed disgust as a way of averting our attention from the things that remind us of it. But this is not McGinn’s view. McGinn, if I understand him, believes that horror at our mortality and its death-in-life indicators is actually present in disgust, rather than being something that disgust protects us against: this is the real cognitive content of the emotion. What determines whether such an interpretation is correct?

Clearly McGinn hopes that we will recognize its correctness introspectively, once it is formulated; that is the method of phenomenology. But I have to say that, while his account of our metaphysical predicament and of our feelings about consciousness, physical vulnerability, and death is very convincing, I cannot find these thoughts buried in the emotion of disgust—though I cannot speak for others. There may be an analogous problem for the verification of Rozin’s hypothesis, depending on one’s view of the retrievability of the unconscious, but it is more of a problem for McGinn’s theory, because he is not postulating an unconscious mechanism of repression. He is describing what we see in disgusting things when we find them disgusting. He says we see the absurd organic destructibility of consciousness, and inevitable death.


Kelly’s account is radically incompatible with McGinn’s since Kelly holds that disgust per se has no meaning—neither the meaning McGinn attributes to it nor any other. Its unity is that of an identifiable syndrome of response—facial expression, revulsion, and a sense of contamination—that can attach to a wide range of objects. An important part of Kelly’s ground for believing this is the fact that disgust has been recruited to enforce cultural and moral norms far away from its organic home base.

McGinn mentions moral disgust and disgust over shoddy performances, bad writing, and so forth, but he sets these aside as metaphorical uses of the term. Kelly insists that moral disgust is not metaphorical, that it is the same visceral response, with the same characteristic facial expression. Perhaps “metaphor” is not the right word, but I agree with McGinn that moral disgust is a different phenomenon. I may be disgusted when Republicans hold the country to ransom over raising the debt limit, but it is not like what I feel when cleaning up a pool of vomit. It seems rather to be a particularly strong form of contempt, without any of the shrinking away from uncleanness and contamination that belongs to core disgust.

Even if we set aside moral disgust, however, the other type of norm-based example that Kelly cites seems phenomenologically much more like the basic organic case. Violations of religious dietary laws and caste boundaries seem to provoke true disgust in those who have internalized them. Eating pork, for a Muslim, or sharing a meal with an Untouchable, for a traditional upper-caste Hindu, is not just prohibited but polluting. My closest observation of the phenomenon is of mid-twentieth-century American racism and homophobia, which were certainly supported by feelings of disgust. And as the norms change in response to cultural transformation, the disgust reactions fade and gradually disappear.

Kelly seems to me right to argue that what we have here is the co-opting of a ready-made form of aversion to enforce conventions whose source is completely different. It is not clear how the co-opting comes about, but any norm that requires avoidance of contact, particularly with something not directly harmful, is suited to enforcement by disgust.

McGinn does not discuss these cases, and he might argue that they too are metaphorical, or analogical extensions from the basic case, with its hopeless protest against our grotesque embodiment. If he is right, disgust is a profound emotion. If Kelly is right, the sense that disgust reveals to us the dark truth beneath the surface of life is an illusion. Then again, they might both be wrong. I suspect that disgust means something, as McGinn maintains, but that it has less to do with death-in-life than with the opaque but fragile crust on the surface of the self that is a crucial condition of civilization, allowing us to present to others a carefully controlled and cleaned-up version of ourselves. Reminders of the mess that lies beneath it, and of its vulnerability to penetration, can cause us to shrink away in disgust, even though we also want to break through it sometimes, with sex, or a dish of calf’s brains.