The philosophy of pimples is an underdeveloped subject. Why do we react to them with such revulsion? The other night I was watching TV (Jimmy Kimmel Live, 14 August, 2018) and was treated to some footage of assorted people looking at film of pimples being burst. My philosophical antennae twitched (I have written a book on disgust). The reactions were striking: turning of the head, averting of the eyes, grimaces, expressions of nausea, protests at having to watch this stuff. Why the extreme reaction? It would be hard to maintain that fear of contamination lay behind it, since these were just computer images they were looking at–and why would pimples be carriers of disease? Nor did anyone complain that they might catch something by looking at these images. Yet the reaction of disgust was intense and uniform. So what exactly was their psychological state? Presumably there was some property P such that the subjects of the experiment judged that pimples have P, where P is marked as disgusting: but what is this property P? It can’t just be the whiteness of pimples or their hilly shape or the fact that they can burst and discharge their contents—lots of things are like that and cause no revulsion at all. If plants had pimples, would we be quite so disgusted by them? The physical properties of pimples don’t constitute P; nor does their purely sensory appearance. Occurring on a human body, particularly the face, seems to make all the difference: but why? Why pimples and not freckles?
Theories have been proposed (being out of place, being a reminder of our animal nature, genital connotations, signs of ill-health, tokens of death, unruly life, and so on), but what is striking is that none of this is evident to the subject of the experience. It is not as if the subject responds by citing these theories when asked what he or she finds so disgusting. Instead subjects become strangely inarticulate when asked to explain their disgust reactions, even perplexed. And the theories do not command general assent, as well as being vague and poorly formulated. It is quite a mystery why we find certain stimuli disgusting and not others. So (a) people reliably have disgust reactions to pimples (inter alia) and (b) they don’t know what it is that so disgusts them. Indeed they are certain that pimples are disgusting (especially when squeezed) but they are ignorant about the source of the disgust: they can’t say what it is that triggers their visceral reaction. In the case of fear people can specify why the object produces the reaction of fear, because of the dangers presented by the object, but the objective properties that elicit the disgust reaction are elusive and inscrutable. The puzzle is how this is possible—what the explanation of the ignorance is. Why can’t we say what bothers us so? People are apt to resort to asking, “Can’t you just see that bursting pimples are disgusting?” When pressed to justify their reaction they fall silent, perhaps admitting that they don’t know what to say. 
The Freudian will insist that the reasons for disgust are unconscious, so it is not surprising if the subject can’t access them—as with revulsion at snakes (phallic symbols etc.). But this is not a credible explanation in the case of many disgust objects, including pimples—do we really have repressed sexual emotions surrounding pimples? It is not that we have repressed knowledge of the significance of pimples and that’s why we can’t articulate our revulsion. Nor would it be plausible to assimilate the case to cases of tacit knowledge, holding that we have tacit knowledge of what P is but we don’t have explicit knowledge of it (compare our tacit knowledge of the definition of knowledge, say). This does not explain why it is so difficult to excavate the grounds of disgust—why we can’t complete “x is disgusting if and only if…” Is it perhaps a cognitively unmediated reflex that has no articulation, like the patellar reflex? Does the stimulus just tap into brain circuits that initiate a reaction of nausea without any conceptual mediation? That too seems implausible: why is the reaction found only in mature humans, and why is it accompanied by a judgment of disgust? So the puzzle remains: not just the puzzle of what prompts disgust, but also the puzzle why we don’t know what prompts disgust. Why are we so baffled by our own reactions? It can hardly be that disgustingness is just a primitive property that resists all attempts at articulation—a perceptual simple. Pimples don’t have ordinary perceptible properties and in addition a further simple property of being disgusting. Compare beauty and ugliness: here we can make a shot at saying why we find things beautiful or ugly, but we are not similarly able to spell out our judgments of disgust. Thus we are liable to accusations of irrationality in the disgust case (why do we find mucus and ear wax disgusting but not tears?). Freckles we are fine with for some reason, but pimples powerfully repel us—why? Are we just arbitrarily sounding off?
Here is one thing that seems right to say: when a person is disgusted by something he or she seeks to avoid sensory contact with it. We don’t want to look at or touch or smell or taste the disgusting thing. Again, disgust differs from fear in this respect: we want to flee the fearful object yet we don’t mind observing it from a safe distance, but the disgusting object we want out of our sight whether it is close or distant. The mark of disgust is averting the gaze, as with those pimple viewers I mentioned. And it goes beyond that: we don’t even want to hearabout disgusting things. Embedded in the disgust reaction is a desire not to know—we don’t want to be acquainted with, or cognitively linked to, the disgusting stimulus. We would be happier never to have encountered a disgusting object. It is torture to be subjected to unremitting perception of disgusting objects—feces being the obvious example. Fear is not like this: we don’t desire not to know fearful objects, only not to be exposed to their dangerous tendencies. We don’t find lions disgusting—we are quite happy to gaze at them—but we don’t want to be caged up with a hungry or aggressive lion. So we can say that disgust is anti-epistemic—it is a positive wish not to know. If we are unfortunate enough to witness a pimple burst on someone’s face, we want to forget the experience as soon as possible—we want our memory to fail us. We are against having this type of knowledge. If the inanimate material world produced strong disgust reactions in us, we might not want to know about it (at least we would be ambivalent about physical knowledge); in the case of the organic world, we definitely want to avoid certain kinds of knowledge about it, and might need to be trained to overcome our natural disgust reactions (as with medical training and cadavers).  The central message of disgust is: “I don’t want to know!” This again is rather puzzling: why are there things that we don’t want to know about? Isn’t knowledge generally a good thing? Don’t we want to add to our stock of knowledge? But the thirst for knowledge runs up against an obstacle in the shape of disgust—there are some things we prefer not to know about, especially if the knowledge is by acquaintance.
So there are two epistemological puzzles about disgust: the puzzle of why we can’t formulate what disgusts us, though we make confident judgments about it; and the puzzle of why we prefer to limit knowledge in the way we do. These are to be added to the puzzle of what makes something disgusting, i.e. what its necessary and sufficient conditions are. Pimples are a problem.
 Colin McGinn: The Meaning of Disgust (OUP, 2011). In this book I defend a general theory of what makes an object disgusting, emphasizing death-in-life and life-in-death; in the present essay I take up some ancillary puzzles.
 People can certainly say that slimy things are generally disgusting and that gleaming things are not disgusting, but they can give no general characterization of the class of disgusting objects. They tend merely to list the things that particularly revolt them. By contrast, they have no difficulty saying what scares them, namely dangerous things.
 It is fortunate that our disgust reactions are confined in the way they are: just think how difficult science would be if its subject matter made us want to vomit! What if psychological states elicited disgust reactions? Numbers? It would all be like studying pimples.