We’ve all had that moment while perusing a flea market or junk store when you stumble across an item and have to yelp, “Good lord, that is ugly!” So ugly, in fact, you have to marvel that it even got made in the first place.

But what is it exactly that makes an object ugly? Picture a Rococo room, with every inch covered in scrolling gold ornamentation, crammed with chubby cherubs and vaguely erotic irregular shapes. Do you feel horrified or fascinated? Compare that with the spare, clean lines of Shaker room with simple, elegant wooden furniture. Is it the picture of blissful peace or painful boredom? Does folk art make you cringe, or do you see rough-hewn beauty in its imperfections? Does iridescent carnival glass make you jump for joy or avert your eyes?

You might feel revolted by an object, but if you try to objectively explain why it is ugly, it’s harder than you think. Most people are influenced by the dominant tastes and fashion sensibilities of their generation, class, and ethnic group, and when you remove those factors from the equation, an exact, universal definition of “ugliness” becomes almost impossible to pin down.

British design critic and cultural commentator Stephen Bayley was up for the challenge, writing a book called Ugly: The Aesthetics of Everything, first published in 2012. But as Bayley—who is unapologetically obsessed with his Modernist version of beauty—delved into the process of examining what he and others consider ugly, he found that the ugliness would vanish.

“It’s a book of questions rather than answers,” Bayley tells me on the phone from London. “When you start thinking about defining beauty, it disappears. It’s like trying to embrace fog. Same goes for ugliness—the idea is as slippery as an eel.”

Still, everyone has an intuitive sense of ugliness—things we find troubling, aggressive, or annoying—and we know it when we see it. “We all know what ugly really means,” Bayley says. “The English word comes the Old Norse word, ‘uggligr,’ which means ‘aggressive,’ which is why we talk about an ‘ugly customer’ in English. Ugly things are things which we find disturbing. But at the same time, disturbing things are also interesting.”

Ugliness is also surprisingly hard to design on purpose, as Bayley discovered both teaching and speaking with architecture students. “If you give a class of architecture students a project, saying ‘Please design an ugly building,’ they actually find that difficult. It’s very difficult to create ugliness, although you wouldn’t believe it by walking around in any big city. Ugliness often is just an accident, but it’s often utterly fascinating.”

“Lots of people agree that guns are beautiful, but they have a functional purpose which most people find repellant. What sort of beauty is that?”

Reading Ugly, it’s not too difficult to suss out Bayley’s personal preferences: He’s all about clean lines, right angles, and functionality; he finds neutral colors and the natural tones of wood more tasteful than bright hues or shiny things. He’s got no use for elaborate glass paperweights, loathes taxidermy and all Victorian hobbies that attempt to capture and catalog nature, finds tattoos tacky, and has no patience for mid-Century kitsch relating to Elvis, Vegas, or tiki bars—things like aloha T-shirts, souvenir mugs, or velvet paintings.

“I’m aesthete at heart,” confesses Bayley, who also published a book called Taste: The Secret Meaning of Things in 1992. “I’m one of those people, for good or for bad, who determine the value in anything by its appearance. People think appearance is superficial. I don’t. I think appearances matter, and actually the classical Greeks felt the same. They thought beauty had a moral character. That’s my fundamental view of the world. I can’t walk down the street and not be both exhilarated by beautiful cars and beautiful buildings and dismayed and depressed by ugly cars and ugly buildings. I am just one of those poor souls.”

As the creator of the Design Museum in London, Bayley is clearly partial to the aesthetic principles of Mid-Century Modernism. But working on Ugly, he set out to challenge his own biases.

“One of the assumptions of the Modern design movement is ‘We’re now working to beautify the world. We’re going to make it more lovely. We’re going to make it clean, hygienic, and right-angled’—which I quite like,” he says. “All I’m doing is asking some questions about that beauty that people were trying to make democratic, what it actually was, and what it actually means. I’m less and less certain about how to define it.”

While history is jam-packed with philosophical books—not to mention art, poetry, fiction, and music—espousing the wonders, mysteries, and power of beauty, academic texts exploring ugliness are rare. “There was a mad German, a follower of the philosopher Hegel, who wrote a book on ugliness in German—which I can’t read—in the 19th century. Then an Australian architect critic called Robin Boyd wrote something called, The Australian Ugliness, a book about Australian architecture, in 1960. And then in 2007, Umberto Eco wrote a book in Italian called Storia Della Bruttezza, or ‘the story of ugliness.’ It’s a fabulous book, as Eco’s books always are, but it’s actually not about ugliness. He’s written about grotesques, freaks, and monsters.”

Bayley explains that researchers studying “neuro-aesthetics,” which he calls “this new almost pseudo-science,” are attempting to map the human brain’s response to what’s lovely and what’s repulsive. But scientists have been attempting to quantify beauty for ages.

As far as we know, ancient Greek mathematicians like Pythagoras and Euclid were the first to calculate what’s known as the Golden Ratio, an aesthetically pleasing pattern found often in nature. Centuries later, a medieval Italian mathematician named Leonard Fibonacci gave the ratio a numerical sequence. It’s found in the petals and seed heads of flowers, in pinecones and pineapples, in tree branches, nautilus shells, spiral galaxies, human faces, animal bodies, and DNA sequences. It’s also the basis of classic Greek and Renaissance architecture.

“The Golden Ratio or the Golden Section works out roughly as the ratio of 8:13,” Bayley says. “The idea is that in architecture and design, and in painting, too, we find that 8:13 proportion pleasing because it corresponds, more or less, to the field of vision of the human eye. That’s the theory. Certainly, a great deal of architecture is based on the Golden Section. But we find a lot of other things pleasing as well.

“The best book about beauty is 2001’s On Beauty and Being Just by Harvard professor Elaine Scarry, who says if something is beautiful, we want to reproduce it because we want more of it,” he continues. “Shakespeare says exactly the same thing, ‘From fairest creatures, we desire increase that therefore beauty’s rose might never die.’ That might be an inverse way of defining what ugliness is: When we see something ugly, we want less of it.”

Paradoxically, if every single thing in the world were flawless and perfectly proportioned, humans would be miserable. In fact, too much perfection can even be disturbing, as scientists discovered when they introduced people to humanoid robots too flawless to be real people. The theory of the “uncanny valley” explains why people are revolted by simulations that are “almost human” but not quite. Similarly, Bayley finds ugliness absolutely necessary.

“If the whole world was beautiful, however defined, nothing would be beautiful,” Bayley says. “If every man on earth looked like George Clooney, it would be appallingly boring. If every piece of furniture were designed by Dieter Rams or whoever your favorite designer is, it would be dull.

“We need variety and we need strife. We need aesthetic conflict. In this sense, ugliness may be a very good thing. We need a certain measure of ugliness in order to enjoy the beautiful. But how much ugliness do we need? Should 30 percent of the world be ugly, or 40 percent? I don’t know.”

During the Industrial Revolution from 1760 to about 1840, cities in Europe and then the United States became ugly, odorous places, as factories full of clanking machines spewed smoke and soot. More people taking new factory jobs crammed into apartments and tenements and piled more stuff onto the growing mounds in the streets, which were already covered in horse excrement. With factories producing cheap trinkets anyone could afford, Victorians were making more and more waste with no place for it to go.

As a result of Industrialization, traditionalists like 1800s social critic John Ruskin mourned the old days, Bayley writes, of the spinning wheels, oaken linen presses, and hand-carved Windsor chairs. Even electric light was thought to be ugly, exposing every imperfection with its harsh brightness. The railroad tracks that were sprawling out to the far reaches of the country were seen as an invasion of untouched nature and a blight on the landscape. Later, railroadiana and even industrial factories and machines were thought to possess a beauty all their own, particularly as photographed by Bernd and Hilla Becher in the late 20th century.

Rejecting the ugliness of 1770s factory-town Manchester, a woman called Mother Ann Lee led her radical Christian sect, United Society of Believers in Christ’s Second Appearing, to New York state in 1774. Known as the “Shakers,” they advocated celibacy and believed that ecstatic dance involving shaking and trembling would purge them of sin. Lee, like the Greeks, believed that aesthetics revealed one’s morality. Because clean lines were closer to godliness, her sect became known for its simple, elegant handcrafted wooden furniture, boxes, baskets, and buckets.

“I love it that Mother Ann Lee, who was a poor, working-class girl from Manchester in the north of England, somehow managed to get the money together to make a passage to New York, where she sets up this extraordinary community,” Bayley says. “We don’t know, but it’s reasonable to speculate that Mother Ann Lee had been sexually abused as a child and certainly grew up in terrible, filthy conditions. Thinking about how she left the horrors of Manchester to the bright uplands up in New York state, Ann Lee said, ‘There is no dirt in heaven.’ Isn’t that beautiful? Shaker furniture was proto-Modernism. What Modernism really means is an overwhelming desire to make things tidy, and certainly the Shakers had that.”

Other religious sects embraced this idea of sacred perfection. The free-love-practicing Oneida Community, in fact, was even known as “The Perfectionists.” Founded in New York state in 1848, its craftsmen developed what they believed to be the perfect shoe, known as The Final Shoe, as well as the Lazy Susan table—later, they became known for their fine silverware. Other artisans didn’t have a spiritual epiphany, and they simply detested highly ornamented machine-made furnishings. This led to the anti-industrial Arts and Crafts movement starting in 1860 that promoted handcrafted furniture, metalwork, wallpaper, textiles, and jewelry in simple, symmetrical, and natural styles.

Like these purists, Bayley has no patience for what he calls “featurism” or “superficial beautifying,” “the enemy of understatement and plainness.” (“Plain,” interestingly enough, is the British euphemism for “ugly” when applied to a woman.) Victorian-era mass-produced goods—in Ugly, Bayley cites fussy, overwrought chairs and biscuit tins with Gothic molding—were nothing if not embellished. This is because for the first time, regular people, and not just very elite few, had disposable incomes. Working-class workers wanted things that telegraphed status, even though they couldn’t actually afford luxury goods.

That’s what created the market for “kitsch,” particularly was Bayley calls “fancy goods,” and led to the development of imitation leather and wood, as well as fake ivory, horn, and tortoiseshell. “There are different sorts of kitsch. There’s unconscious kitsch of the rude, vulgarian, uneducated classes, and then there’s the knowing kitsch of the sly and callous operator in the field of taste. I describe kitsch as cynical rubbish, which patronizes the consumer.”

“It’s very difficult to create ugliness, although you wouldn’t believe it by walking around in any big city. Ugliness often is just an accident.”

In his book, which Bayley says is slightly tongue-in-cheek, he reiterates this complaint that the democratization of consumption meant that objects were made to attract the broadest consumer base possible, by appealing to the lowest common denominator—the same criticism social critics have launched at television programming for decades. Still, Bayley’s assertion that people who lacked wealth, education, or refinement created the market for ugly things doesn’t sit quite right: After all, wasn’t it wealthy royals that created the most unbearably garish gilt and bejeweled Rococo palaces in the 18th century?

“Before industrial production, only the very rich could buy discretionary goods. Everybody else subsisted on craft production,” Bayley explains. “But the Industrial Revolution turned everybody into consumers, and everything became an episode in the history of taste. Bernard Berenson, the great art historian, once said that taste begins when the appetite is satisfied. And that’s what happened, really, in the 19th century to a very large degree: The appetites of these new consumers were satisfied.

“In 1899’s The Theory of the Leisure Class, Thorstein Veblen makes the point that as soon as any society moves beyond subsistence, they buy goods which are status symbols,” he continues. “That’s what fancy goods are. We still buy them now, but they’re called brands. Veblen had coined the term ‘conspicuous consumption,’ which is the sort of consumption you do when you’re buying stuff you don’t need. Our economies depend on that concept.”

And so, middle-class Victorians filled up their homes with knick-knacks and “conversation pieces” like art glass paperweights, which, Bayley writes, “represent in miniature the nineteenth-century attitude to design: at once marvels of the industry, but also aesthetic horrors. … If the public had a morbid appetite for the marvellous, then the industrialist and entrepreneurs who manufactured paperweights were well able to stimulate and satisfy it.”

A glass paperweight or novelty snowglobe might have contained a piece of real nature such as a flower or seahorse—a part of the bizarre Victorian trend for collecting “natural” curiosities often made by the very factories that were destroying the environment. It’s as if people were trying to freeze or pin down fleeting natural phenomenon by buying butterflies pinned in cases, bugs trapped in amber, taxidermied animals, aquariums, ferns in Wardian cases, or scrapbooks to collect seaweed and dried flora—while accelerating the erosion of the actual natural world.

Victorians were well aware of their own excesses and ridiculousness. In 1852, Henry Cole, the founder and director of the institution that became known as the Victoria and Albert Museum, opened a Gallery of False Principles demonstrating bad design, which came to be known as the extremely popular “chamber of horrors.” In a 2001 article in the Guardian’s magazine, Sarah Wise describes the collection containing things like a pink bottle shaped like a snake, a flower-pot shaped like reeds tied with a yellow ribbon, scissors shaped like a stork, a morning-glory shaped gas-jet lamp made of glass and gilt brass, a jug in the form of a tree trunk, a chintzy papier-mâché tray, and blindingly busy wallpaper.

In Germany, museum curator Gustav E. Pazaurek followed in Cole’s footsteps, opening his “Cabinet of Bad Taste” at the Stuttgart State Crafts Museum in 1909 to demonstrate what he considered design mistakes. His catalog of design offenses includes anything made of fur, bones, or teeth; animal trophies; material used to imitate other materials; mass-produced objects aping handcrafted ones; manic ornamentation; lies of function; odd proportions; sharp edges; excessive iridescence; anachronisms; design imitating foreign cultures; fake folk art; jingoistic, religious, racist, or sexist kitsch; and toys that harm children.

To rid the Machine Age of all this bad design, the first waves of Mid-Century Modernism arrived as the Bauhaus school in 1919 and as Art Deco, or Streamline Moderne, in 1925. This time, the elite, educated world of design would beautify and simplify common mass-produced consumer objects, offering the unwashed public top-down taste, through lovely and uncomplicated things such as Catalin radios and Bauhaus chairs.

“Mass-produced stuff doesn’t have to be ugly,” Bayley says. “Mass production requires standards, and standards lead to excellence, or so Le Corbusier believed. Mass production frequently leads to elegant and pleasing solutions. That’s the whole story about the adventure of Modern design. It was meant to make beauty commonplace and democratic. That’s a wonderful idea.”

For example, iconic designer Raymond Loewy even transformed household machines, such as the Coldspot refrigerator, Coke dispenser, and Singer vacuum cleaner, into chrome-trimmed works of art during the 1940s and ’50s. In 1956, according to Ugly, Dieter Rams reached the apex of Modern idealism with the radio-turntable dubbed “Snow White’s Coffin.”

In the 1950s and ‘60s, the sleek, efficient, and futurist look of Mid-Century Modern was absorbed into corporate culture, as it dominated offices adorned with Knoll furniture. Buildings made in the Modernist subset known as Brutalism—so named after the French phrase beton brut, meaning “raw concrete”—were heavy, large, imposing things with jutting angles that look appalling to people now.

“Most people do find Brutalism unattractive today,” Bayley concedes. “But in England, there’s a change of taste. That’s why I put England’s most famous Brutalist building, the Trellick Tower in West London, on the back jacket of my book. It’s recently been listed by English Heritage as a building of national historic architectural importance. Any minute now, I promise you, Prince Charles, who used to condemn these things, will be telling us that Trellick Tower is a thing of beauty.”

During the mid-century, people fed up with the grim, sterile, and business-like aspects of Modernism embraced a new, more self-aware kitsch and the “faked sensations” of tiki bars and restaurants, Las Vegas, and Disneyland. Punks in the 1970s rebelled even further, rejecting clean, commercial ideals of beauty by making themselves aggressively ugly with mohawks and safety-pin piercings. All the while, cities only got uglier with the spread of strip malls, fast-food chains, and mobile-home parks completely unconcerned with aesthetics.

“We need a certain measure of ugliness to enjoy the beautiful. But how much do we need?”

American pop-culture writers Jane and Michael Stern amused themselves documenting the fruits of the new tacky kitsch culture, the 20th century’s own “chamber of horrors,” in their 1990 book The Encyclopedia of Bad Taste. In Ugly, Bayley names a few of his worst offenders from their book’s content page, including novelties and gags; Aloha shirts; bobbleheads; Tupperware; artificial Christmas trees; tattoos; Troll dolls; polyester; Day-Glo; macramé; pet clothing; shag rugs; snowglobes; reclining chairs; and candle art.

One list item, “Breasts (enormous)” seems like body-shaming, until you realize the Sterns are not talking about living, breathing women themselves. Instead, they’re referring to the U.S.’s national obsession with objectifying big breasts by depicting them on actual inanimate objects from Barbie dolls to girlie glasses and beach souvenir mugs shaped like disembodied boobs. Certain car bumpers were even crassly dubbed Dagmars, because they resembled the ample bust line of a 1950s actress Virginia Ruth Dagmar. All this unseemly and sexist leering makes people in the elite design world cringe. But at the same time, they consider it tasteful and not at all gratuitous these days to expose small breasts on runaways and in fashion shoots, what some critics have dubbed “fashion tits.”

Today, Apple products like iPhones, iPads, and MacBooks embody Bayley’s ideals of elegant and functional design, but, he says, Apple will soon have no choice but to make them more gaudy. “Apple’s run out of ideas aesthetically,” he explains. “You can’t make anything more pure than the current iPhone or iPad. They’re going to have to go Baroque—which they’ve already started to do. You see it with their new products, like the iPhones in bright colors. Their English senior vice president of design, Jonathan Ive, is a brilliant guy. What he’s doing is ultra-sophisticated. He created these technologically dense products using a craftsman’s technique and skills because his father’s a silversmith and he actually knows how metal works. These lovely things in our hands are only apparently simple. They’re in fact extraordinary. They’re not utilitarian at all, but incredibly subtle and contrived. I promise you, in five years’ time, they’ll be very different.”

While mocking American junk culture may seem like good sport, it lacks a certain degree of sympathy for lower-class Americans, who might have seen velvet paintings or Marüshkas as an affordable way to decorate their homes, who can’t afford a trip to Europe but can afford a trip to Vegas, who can budget for Wal-Mart groceries and fast food but not Whole Foods or fine dining, who see Tupperware as a thrifty way to keep leftovers from spoiling. In some communities, buying the shiniest, flashiest clothes or cars might be a popular and accepted means of celebrating success.

In other cultures around the world, the bone-colored paint and bare wood that Bayley described to me in his spare, elegant home—the picture of refined taste in the Western World—would be seen as egregious. For example, in countries like Mexico and India, bright colors are a vital part of the residents’ lifestyles. In particular, India is known for its breathtaking and elaborate textiles and gold ornamentation. Bayley, for what it’s worth, owns up to his myopia.

“The idea of ugliness is as slippery as an eel.”

“I’m afraid I personally live in what’s predominantly a white, middle-class, educated Anglo Saxon world, which is the world I’m addressing,” he says. “My education and liberal background make me inclined to believe that, yes, well, green crocodile-skin shoes might be immensely pleasing to certain ethnic groups, but they’re not terribly pleasing to me. It goes back to taste again. Taste is a mixture of inherited attitude and proclivity and ideas we acquire though our education and our social and ethnic backgrounds.

“We middle-class educated WASPs, we’re all terribly repressed—no doubt about that,” Bayley continues. “That’s why I wrote Ugly, you see, to overcome my repression. I’m not looking so much at the dark side of things; I’m looking at the colorful side. Trying to define beauty defeated Plato, Immanuel Kant, and every other great philosopher. No one’s ever bothered to define ugliness because it can’t be done. All I’m saying in this book is ‘Look, have a think about this. Are you certain about what you believe is correct?’”

Writing Ugly, Bayley ran smack into another contradiction: If good, functional design with clean lines telegraphs high morals, then what about the Colt .45, “the gun that won the West,” which functions excellently? Many beautiful, astounding objects have been designs for “ugly” purposes, such as death, war, and mass destruction. Colt .45s and other machine-made guns in the 1800s were sometimes embellished—plated in gold or silver and hand-engraved with intricate designs.

“Again, I’m undermining some of the assumptions of the Modernist movement, which said anything well-designed would be beautiful,” Bayley says. “That’s clearly not true, because a lot of things which work very well like oil refineries, few people find them beautiful. Equally, with things like guns and military aircraft, lots of people would agree that they’re beautiful, but then they have a functional purpose which most people find repellant. That’s why I wrote the little chapter about the B-52. What an amazing machine. It’s awe-inspiring, the technical mastery it suggests. I personally find it a physically beautiful thing as well, with lovely shapes and details. But this beautifully designed machine was created in order to cause destruction. What sort of beauty is that?”

Perhaps truth is not beauty, after all.

(To read more, pick up Stephen Bayley’s “Ugly: The Aesthetics of Everything” at Overlook Press. Find more of Bayley’s books at his web site.)