School was out for the summer, and Princeton University was embarked on Reunions weekend 2009, a three-day bender amounting to a tribal rite. The institution and I were drunk. The last Thursday in May had just become Friday when a DJ put on Fatman Scoop's "Be Faithful," and a rumble of arm-waving club rap echoed through the New Jersey night.

Single ladies—I can't hear y'all! Single ladies—make noise! The single ladies made noise indeed, a few by crashing through folding chairs en route to the dance floor. This carnival welcomes all alumni back every single year—I graduated in '96, and this was my thirteenth—but especially those celebrating "major reunions," the fifth, tenth, fifteenth… These classes host keg parties on the lawns below the Gothic dormitories, gargoyles leering down at 20,000 revelers. The class of 2004 had rented this particular party tent, but the class of 2009, five days shy of graduation, owned the night.

Who fuckin' tonight? Who fuckin' tonight? Who fuckin' tonight? The single ladies slurped one another's faces, and my eyes popped at the mileage on my own odometer. It was the case in my time that a scant two minutes of no-frills grinding to a Prince song could provoke a full two days of scandalized gossip. The ladies of '09 had their hands on the floor and their asses in the air, bucking at crotches on the upbeat. My companion, a Dutch photographer, lit up with delight. When he started bounding around like a gun dog, I decided to name him Shooter.

Who fuckin' tonight? Who fuckin' tonight? Who fuckin' tonight? An older guy—identifiable by the pattern of his orangeand-black blazer as an '84—wiggled his head to the groove, bald spot mirroring red light. A girl in a white miniskirt rocked out by back-kicking with a bandaged ankle while swinging on crutches. Behind the cage for the sound engineer's booth, a kid pissed in a cup, tucked himself in, popped his collar, and briefly humped the nearest girl. This was the warm-up night for an elite bacchanal, the perennial blowout kegger of the Ivy League.

Long before becoming a world-class university, Princeton was an extraordinarily boisterous party school. The college was founded in 1746 by frowning Presbyterians who shortly thereafter issued a ban on "tavern haunting," initiating a tradition of crackdowns on drinking now in its third century of utter futility. Every time I go back to the campus, I smile fondly at hedges I once napped under, windows I vomited from, astronomy departments I hooked up in.

Reunions weekend is probably the largest regular alumni gathering in the world. Historically, the level of alcohol consumption here exceeds that of every other event in America save the Indy 500. The school mascot is the tiger, and Reunions is defined by blackout drunkenness and blaze orange disorder. To be clear, not all of the events directly involve getting shitfaced. The schedules are dense with memorial services and prayer services and community-service projects. But really, the main point is getting shitfaced. Anthropologists refer to this kind of debauchery—bonding by way of getting smashed—as the pursuit of conscious excess. The multigenerational aspect heightens the sense of disappearing into a tradition and a collective identity. The most passionate Reunions fan I know—a '97 who hasn't missed a year since first sneaking in as a freshmen—opines that the profusion of ridiculous costumes we wear encourage the event to become "a platform for creative absurdity."

The valedictorian of Princeton's great class of 1905 was Norman Thomas, a clergyman and civil rights activist who ran for the presidency six times on the Socialist ticket. He had a theory that Reunions was essentially a beer-tap time machine. "Some things in life justify themselves emotionally, without necessity for analytic reasoning," he once wrote. "On the whole, Princeton reunions fall in that category. In my moralizing moments, I may regret that reunions are too greatly inspired by the prayer: 'Make me a sophomore again just for tonight,' which…with the aid of a sometimes excessive consumption of the spirituous, rather than the spiritual, often seems to be granted." Throwing himself into Reunions weekend, an alumnus travels to a giddy dimension where his youth never really ended and never really will.