Some philosophers doubt that there is such an emotion as disgust, yet in spite of the concept's overlap and fuzzy edges, there is a learned discourse about disgust defined as a feeling of revulsion. The prime example is in the context of food. Disgust may cause shock, faintness, even vomiting, or at the least it may dull the appetite. Not only to taste, but also to smell putrefying flesh, to touch excreta or slime, or even to set eyes on an open wound may provoke disgust. As a form of strong rejection, disgust is not the antithesis of desire; its effects are too immediate, even unexpected and uncontrollable, like an instinctive reaction. Why should humans be equipped by nature with this capability?
Training
A social explanation of disgust focuses on nutrition and the need to train children to avoid known poisons. Babies are taught by their parents' expressions of disgust not to eat noxious things. From the classifying of foods as edible or disgusting, the idea is extended to reprehensible behavior and despised classes of people. The ascription of filthy doings to outsiders accords with theories about the construction of ethnic identity. This approach allows for local differences due to training: some people reject snakes, worms, live grubs, or mud as food, but others relish them. Cannibalism evokes widespread disgust except among cannibals.
The limitation of the social training explanation is that the things commonly regarded as disgusting are not especially harmful. The people who habitually eat what others call disgusting would seem to enjoy as much good health as their critics. Furthermore, if early training in discriminating nutritious food explains disgust, the training is inefficient: it lets pass a lot of poisonous plants, roots, and living organisms.
Hygiene
The work of Louis Pasteur (1822–1895) and Joseph Lister (1827–1912) on microbial infection gained new relevance to disgust through the revival of Darwinism. An approach via hygiene starts from finding a strong convergence of evidence across the world to show that disgust is a direct response to waste products of the human body, including feces, slime, spittle, pus, mucus, and phlegm, which may carry infection. The same feeling of revulsion is extended to eating similar products of other living organisms and to anything that suggests these body wastes, like snails, slugs, and bugs. Evolutionary biology suggests a genetically inherited disgust mechanism that protects from infectious diseases.
Both the social training argument and the biological argument are open to the objection that the risks of disease from eating sick animals are only probabilities. House flies, mosquitoes, rats, and lice are dangerous to the same degree of probability, but they provoke more annoyance than disgust in those they afflict. Many deadly poisons are not slimy and are quite unlike body wastes, and comparative evidence is missing.
The evolutionary approach invites interesting comparisons. Animals may feel disgust, but the theory of genetic inheritance needs to take account of the exceptions. Many female mammals habitually dispose of afterbirth, smelly, sticky, and slimy as it is, by eating it. Hares and other coprophagous ruminants eat their own feces as part of the normal process of digestion. Sows are known to eat their young. Carnivorous animals do not discriminate between the best cuts and the messy-looking entrails, and some species subsist mainly on carrion.
These two approaches to human disgust conflict, and each side can reproach the other for using selected evidence. The social theory focuses on what the biological theory regards as exceptional, and the biologists focus on the common behavior, discounting the exceptions. Obviously, inherited feelings of revulsion can be overcome by training. Cannibals are trained to surmount disgust at eating human flesh, as are those who enjoy mucus-like turtle soup, slimy innards, snails, live grubs, and sticky buns. If no evidence against the thesis is allowed to count, the argument must come to a standstill.
Both arguments are causal and teleological. Both downgrade the importance of this emotion, taking it to be designed (inefficiently) to achieve a limited objective. Neither explains why the onset of disgust should be so sudden or so violent, liable to rack the whole body. Apart from causal thinking, there is analogy.
Analogy
A new direction in brain sciences challenges the separation between mind and body (Damasio). In continuous interaction, physical and intellectual energies sift through a succession of images and order them by creating analogies. Instead of looking for specific functions, analogists look for interactions between a system and its parts. Instead of starting with nutrition, analogists start with the body-mind relation and ask how disgust responds to pressures from the cognitive system.
Analogy maps similarities, checks similar patterns for structural consistency. It is a precarious process of reasoning, like trying to hold a pattern steady in a shifting kaleidoscope. The number of possible analogies for any one pattern is infinite, and the pattern always threatens to dissolve. Only repeated enactment entrenches an idea. Entrenchment needs to be fortified by a mechanism of rejection that protects the established pathways from slippage. The digestive organs are the root for making sensations of disgust analogous to other contexts of rejection and for extending disgust to moral or social contexts. Disgust churns the stomach and produces nausea and a cold sweat. Interacting with the cognitive system, its various vivid analogies are a team of watchdogs protesting against changes that, if adopted, would tumble the edifice laboriously constructed by experience.
One of the side effects of disgust may be to reduce the risk of infectious food. Its main function is in the body-mind system, where it limits conceptual slippage. Disgust warns against concepts threatening dangerously to slide between categories.
Bibliography
Curtis, Valerie, and Adam Biran. "Dirt, Disgust, and Disease: Is Hygiene in Our Veins?" Perspectives in Biology and Medicine 44 (2001): 17–31.
Damasio, Antonio R. Descartes' Error: Emotion, Reason, and the Human Brain. New York: Putnam, 1994.
Goodman, Nelson. "Seven Strictures against Similarity." In Problems and Projects, pp. 437–447. Indianapolis: Bobbs-Merrill, 1972. Reprinted in How Classification Works, edited by Mary Douglas and David Hull. Edinburgh: Edinburgh University Press, 1992.
Mitchell, Melanie. Analogy-Making as Perception: A Computer Model. Cambridge, Mass.: MIT Press, 1993.
—Mary Douglas
