But MOOCs are controversial, and debate has grown louder in recent weeks. In mid-April, the faculty at Amherst voted against joining a MOOC program. Two weeks ago, the philosophy department at San José State wrote an open letter of protest to Michael J. Sandel, a Harvard professor whose flagship college course, Justice, became JusticeX, a MOOC, this spring. “There is no pedagogical problem in our department that JusticeX solves,” the letter said. The philosophers worried that the course would make the San José State professor at the head of the classroom nothing more than “a glorified teaching assistant.” They wrote, “The thought of the exact same social justice course being taught in various philosophy departments across the country is downright scary.”

Nagy has been experimenting with online add-ons to his course for years. When he began planning his MOOC, his idea was to break down his lectures into twenty-four lessons of less than an hour each. He subdivided every lesson into smaller segments, because people don’t watch an hour-long discussion on their screens as they might sit through an hour of lecture. (They get distracted.) He thought about each segment as a short film, and tried to figure out how to dramatize the instruction. He says that crumbling up the course like this forced him to study his own teaching more than he had at the lectern.

“I had this real revelation—I’m not saying ‘epiphany,’ because people use that word wrong, because an epiphany should be when a really miraculous superhuman personality appears, so this is just a revelation, not an epiphany—and I thought, My God, Greg, you’ve been spoiled by the system!” he says. At Harvard, big lecture courses are generally taught with help from graduate students, who lead discussion sessions and grade papers. None of that is possible at massive scales. Instead, participants in CB22x enroll in online discussion forums (like message boards). They annotate the assigned material with responses (as if in Google Docs). Rather than writing papers, they take a series of multiple-choice quizzes. Readings for the course are available online, but students old-school enough to want a paper copy can buy a seven-hundred-and-twenty-seven-page textbook that Nagy is about to publish, “The Ancient Greek Hero in 24 Hours.”