What is Disgust? Kelly '97 Offers New Answers

Yuck! Book Cover

April 9, 2013                                    

BLOOMINGTON, Ill. – Humans know disgust when we experience it  – the sense of revulsion after accidentally drinking spoiled milk or discovering the contents of the baby’s diaper on our hands.

But Illinois Wesleyan University alumnus Daniel Kelly ’97 argues there is much more to disgust than a scrunched-up face and waves of nausea. He discusses the character and evolution of disgust in his book Yuck! The Nature and Moral Significance of Disgust (MIT Press), taking the reader on a journey from understanding why humans naturally avoid rot and toxic foods to the question of why we avoid certain people.

Now an associate professor of philosophy at Purdue University, Kelly became interested in the topic, in part, after a conversation with his graduate advisor over a Chinatown meal of blood tofu and duck tongue soup. His advisor savored the food; Kelly, not so much.

Kelly drew from numerous disciplines – from cognitive neuroscience to normative ethics – to explore the emotion.  Disgust was formed from two previously distinct psychological systems, according to Kelly. One system was designed to protect humans against consuming poisonous foods, and the other was designed to protect against catching infectious diseases. These two systems have fused into what is now recognized as a single emotion, according to Kelly.

“This fusion, it appears, didn’t happen in other animals, even our closest primate relatives, so they don’t have disgust in their psychological repertoire,” Kelly said.  

The ethical side of the topic comes into play when considering the social and moral issues on which disgust has been brought to bear, according to Kelly. He argues that as humans became more social, disgust was recruited to play a number of roles subliminally influencing certain moral judgments. The book makes the argument against invoking disgust in the service of moral justification.

“Recent debates about the role disgust deserves in ethical thought have been impoverished by an inadequate understanding of the emotion itself,” Kelly writes in Yuck!

Disgust’s role in morality should be minimized by society, in part because humans tend to dehumanize what they find disgusting, Kelly said. As a matter of fact, disgust is sometimes enlisted into psychology of morality, but it’s not a fact we should celebrate, the author said. As a matter of ethics, we shouldn’t grant the emotion any kind of moral authority, said Kelly.

“The mere fact that a practice is disgusting to you or anyone else doesn’t provide a good reason or justification in support of the claim that the practice is morally wrong,” said Kelly. “As powerful and vivid as that yuck feeling can be from the inside, the mere activation of this emotion is really just irrelevant to whether or not your moral assessment of the practice that triggers it is correct or justified.”    

Just released in paperback, Yuck! was featured in The New York Review of Books and has received positive reviews in numerous academic journals. In the Times Higher Education, for example, reviewer and British moral philosopher Simon Blackburn wrote: “I found it hard to put this book down, and recommend it as a shining example of genuine progress in moral philosophy, arising from bona fide increases in our understanding of who and what we are.”

Daniel Kelly
Daniel Kelly

Kelly’s interest in philosophy hearkens back to his first year at Illinois Wesleyan. “I came to Wesleyan as a computer science major, and one of the things that was so great was that I had a chance to take classes in topics I was genuinely interested in,” Kelly recalled. An introductory philosophy class resonated with Kelly, who eventually double majored in philosophy and English literature.

“At Wesleyan you could engage in the frank discussion of ideas, and professors were very much a part of creating that environment,” Kelly added. “It was a real joy to be able to argue with friends about things ranging from Hamlet’s soliloquies to scientific realism to the best Beatles album  – and a lot of those conversations continue intermittently today.”

Kelly said his post-Wesleyan plans were “entirely and weirdly Jack Kerouac-influenced. My whole post-collegiate plan was to hit the road and wander far afield -- geographically, culturally, experientially – making sure I had an interesting biography by the time my number came up.”

After a year of travel, Kelly applied to graduate school in philosophy at Tufts University in Boston. “I had been the kind of person who went to school for fun, and at Tufts I decided to buckle down and see how far I could take this thing,” referring to his desire to learn more about what makes people tick and his dawning realization he could even be paid for studying and eventually teaching such a thing.

Yuck! grew out of Kelly’s dissertation at Rutgers University, where he earned a Ph.D. in philosophy in 2007. “The project provided a perfect opportunity to do important philosophical work, weaving together the conceptual resources of several different approaches to explaining the operation and evolution of human cognition,” said Kelly.

Since its publication, Kelly has become somewhat of a worldwide media authority on the topic. He’s been quoted on the disgusting aspect of topics ranging from Starbucks’ use of dye from crushed cochineal insects to color its Strawberries and Crème Frappuccino to the use of medicinal leeches and maggots in Indianapolis hospitals. (For the record, the pink dye in a strawberry frap doesn’t bother him. But don’t try to attach a leech to his leg.)

What else disgusts the author? Kelly said he has become sensitized to the emotion of disgust and the use of the word in everyday life. “I’m much more aware of it in public spaces or casual conversations, which is what happens when you write a book and start noticing things with a hyperawareness of the word or the topic,” he said.

Even after years of research, however, some things continue to make Kelly squeamish, namely, jellied moose nose. “I surveyed a lot of foods considered delicacies around the world, but that one still makes my skin crawl when I imagine putting it in my mouth,” he said.

Contact: Kim Hill (309) 556-3960,