If you want to start taking classes at an Ivy League university unenrolled and undetected, says Guillaume Dumas, a 28-year-old Canadian, start with big lecture courses. If you must sit in on a smaller seminar class, it’s important to show up consistently starting with the first session, instead of halfway through the semester. Also, one of the best alibis is that you’re enrolled as a liberal-arts student. “That's the kind of program that's filled with everything and that you expect people to be a bit weird, a bit confused about what they do,” he says.

From 2008 to 2012, Dumas claims he did stints on a number of elite North American universities—Yale, Brown, UC Berkeley, Stanford, and McGill, to name a few—sitting in on classes, attending parties, and living near campus as if he were an enrolled student. This deception may sound like a lead-up to a true-crime story, but Dumas’s exploits appear to be harmless, done in a spirit of curiosity. "A lot of students are bored in class," he observes, "so if you participate, if you ask questions, if you are genuinely interested in the class, I think the teacher will like you."

I became interested in Dumas’s tale after he emailed me three weeks ago, but I was skeptical, as I would be of any out-of-the-blue note promising a juicy story. Even as I went about confirming what he told me—talking to students he’d met, asking for pictures of him on campus—I didn’t find anything to disprove what he was saying. The facts of his story were not implausible.

More importantly, the concept of his story wasn't implausible either: As tuition costs have skyrocketed, it makes sense that people might try to siphon off some of the benefits of college without paying. While the specifics of what Dumas told me may be hard to confirm, the fact remains that a young adult could conceivably infiltrate a college campus without paying tuition. What might this say about the monetary value of a diploma? And can its component parts—learning, socializing, networking—be unbundled? If so, what would remain?

According to his friends, Dumas is something of a free spirit, and as a teenager was rarely seen without his longboard. His parents didn't insist that he go to college, but Dumas says he began his higher education because he thought he wanted to be a psychologist. He enrolled at a city college in his native Quebec in the mid-aughts. “I started college at 19, and I did that because that's what everybody does,” he says. He started on an academic track to earn a degree in psychology, but he was too intellectually omnivorous to stick with a single discipline.

So he began taking classes in which he wasn't enrolled. “I was just sneaking into classrooms in literature and philosophy and poli-sci and even psychiatry,” he says. Soon, sitting in on classes he wasn't signed up for started to feel natural. “I just found out how to do it. When to hide. What kind of alibi to have or to behave with other students—what to tell, what not to tell,” he says. He erred on the side of staying secretive.

Dumas started taking classes at other campuses nearby: Concordia University, University of Montreal, and McGill University. He started thinking bigger. Providence, Rhode Island, the home of Brown University, was fewer than six hours away by car, and New Haven wasn’t much farther. Dumas says he attended Yale in the spring of 2009, couchsurfing for about a month, and he spent time at Brown too. He says he was taking classes and spending only a few hundred dollars a month, most of it on alcohol for parties. When he later went to UC Berkeley, where he lived at a campus co-op for about two months, his expenses were larger—$600 or $700 a month, in his estimation. While at these schools, he reaped most of the perks of college: learning, partying, and meeting intelligent, like-minded people.

Full tuition at Yale for the 2014-2015 school year, which includes room, board, and books, is $63,250. This breaks down to a little over $7,000 per month during Yale’s academic school year, which means Dumas was getting most of the selling points of college at about a tenth of the cost. At Berkeley, average tuition (which includes in-state and out-of-state students) is about $28,000, but that still works out to more than $3,000 per month. Of course, many students at both colleges receive some form of financial aid, but these are the sticker prices of diplomas there, and many students pay them in full. (This is especially true of international students, who have a much harder time qualifying for financial-aid packages.)

Representatives from some of the schools Dumas attended said that his story is quite rare, though not unheard of. A spokesperson from Stanford said that a student would be asked to leave campus if he or she was attending class without authorization, but added, “Stanford has a relatively small student body and a close-knit student community. It would be challenging for someone to go unnoticed.” Yale’s spokesperson said that someone like Dumas would be trespassing, and noted that he could instead take some of the free courses Yale offers online.

Ollivier Dyens, deputy provost of student life and learning at McGill, explained why his university wasn’t worried about this sort of activity. “Not a lot of people will go through all of this without having some sort of credentials attached to it,” he says. Dyens is right: Most people go to college primarily to get a piece of paper, and learning is something that happens incidentally. The perceived value of a diploma is so high, in fact, that 50,000 fake Ph.D.s are estimated to be purchased every year, a figure only made more striking by the fact that annually, only 40,000 Ph.D.s are legitimately earned.

But according to Dumas, one of the best perks of college that’s available for free is the networking. “I think more than anything it’s meeting people. It's contacts. It's social capital. The kind of people I met in Berkeley or in Yale, I don't know anywhere else in the world with so many smart, cool, open-minded, crazy people can be concentrated,” he says. “And when you think of all the dropouts right now that start companies and stuff, it's all people that didn't need a diploma, that didn't need to pay anything. They went to school to open their minds and meet friends, or meet strategy partners, or something like that.”

From this vantage point, a diploma starts to look a lot like a receipt printed on fine cardstock. It is proof not that one has learned something in college, but that one has paid for it. Without a diploma, how can Dumas prove to anyone—a potential employer, or even me—that he’s undergone an intellectually stimulating experience?

But these days, you don’t need a degree to become wildly successful, as Mark Zuckerberg and countless other young entrepreneurs have demonstrated. Researchers at the Federal Reserve Bank of New York and MIT found that what matters more than anything else in a job application is whether the candidate knows someone at the company.

Dumas himself started a dating service catered toward upscale clientele, and he says it gives him a dependable income. “There’s never been so many career or business opportunities in the world that don’t require a proper diploma,” he says. His thinking aligns with skeptics such as Peter Thiel, whose eponymous fellowship grants young people $100,000 to pursue business ventures instead of studying at a university.

At the same time, the benefits of a college diploma are starkly apparent. As of January, the unemployment rate for Americans who hadn’t finished high school was 8.5 percent. For those who had finished high school but not their secondary education, it was 5.4 percent. But among college grads, this figure was only 2.8 percent. There is the often-cited disparity in earnings as well: In 2012, young adults without a high-school degree earned a median income of $22,900, while those with a high-school degree earned $30,000 and those with a college degree earned $46,900.

Dumas admits that his approach wouldn't work if everyone did it. But he does believe that it could work for some people (just not those who need their degrees to function as technical certifications or licenses, like engineers or doctors). “There might be a better interest in not paying tuition and keeping that money to travel the world and launch a business than having your diploma in philosophy from, I don't know, Johns Hopkins,” Dumas says.

He doesn’t know whether his idea could truly be scaled, but estimates that 5,000 or 10,000 people could follow his lead and go undetected. “I mean, we would not notice,” he says. “They will just disappear in the huge institution.”