The course is called Disc Skills 105, and the instructor describes it solemnly as "a study in human development." But what it is, is Frisbee, the most popular class offered during the past semester on the Arizona State campus at Tempe. Of the 30 undergraduates studying under instructor D. William Williams, none, he says, were just having a fling. "This is no 'cake' course," the 37-year-old prof insists. "Students have to put in time, study and effort. Of course, if you show up—everyone does—and try, you can't fail. That's what's wonderful about Frisbee."

According to its syllabus, though, Disc Skills 105 sounds like an academic challenge fit for da Vinci. Among the subjects it touches on: aerodynamics, airfoils, Newton's law, angular momentum, velocity, gyroscopic theory, weather and flight physics. "Students must understand these concepts to be able to play well," says Williams. "It's very shallow to think we're just out here playing catch. Frisbee is the thinking person's sport." Though courses like his are now offered for credit by at least 40 colleges, Williams is the sport's untitled dean. The world's No. 3 seniors player, as ranked by the International Frisbee Disc Association, he has performed all over the U.S. His earthly possessions include some 400 discs—not all of them bearing the trade name Frisbee—including several antiques valued at $100 each.

To keep in trim for competitions and his twice-a-week course, bachelor Williams rises before 6 a.m., practices Frisbee moves before breakfast, then meditates to shape up his mind. "In terms of physical training, Frisbee is a martial art," he says. "You have to get psyched up. I call it a Zen sport because it is in tune with body, mind and soul."

It is also beginning to take off commercially. There is now a 16-city national tournament circuit, and the annual world championship, which will be held in the Rose Bowl, will boast a $50,000 purse. Among the sport's standard events: the Maximum Time Aloft competition, in which a player tosses and catches a Frisbee thrown like a boomerang (world record: 15.2 seconds); Throw, Run and Catch, in which a player hurls a disc for distance and grabs it himself (record: 271.2 feet); Distance, in which a competitor throws as far as he can (record: 500 feet); Accuracy, in which a person scales a Frisbee at a hoop from seven different spots; and Free Style, featuring an assortment of hotdogging tricks. Team contests include Guts, in which opposing squads zing a Frisbee at each other as hard as they can, and Ultimate, a soccer-like game played on a field with two goals.

The son of a Hollywood, Fla. stagehand and gambler, Williams joined the Marines out of high school, and became an adept boxer and diver. After his discharge, he spent a year at a Fort Lauderdale community college, then worked as a bartender, a contractor and a Yellowstone Park concessionaire. Married in 1966 and divorced five years later, he and one of his two sons moved to Tempe, where he attended Arizona State, earning a teaching certificate in home ec. Hired as an instructor in food service at Phoenix Union High School, he succumbed to the Frisbee bug and later turned pro, supplementing his playing income by working as community relations director for a food co-op. He began instructing at the university on an informal basis in 1978 and managed to get his course accredited this spring. " was a bit hesitant," says Dr. James Odenkirk, head of the physical education department at Tempe, "but he presented himself very professionally. Willie proved to us he could make his course academically worthwhile."

What accounts for the current Frisbee passion, 33 years after the plastic disc's invention? "A lot of kids are turned off by the competitiveness of traditional team sports," explains Williams. "With Frisbee you're competing against yourself. You don't need to be athletic. You can play anywhere. Also, it's nonsexist—some girls play better than boys—and cheap. Most athletic departments spend about $150 to outfit a football player, and a good baseball mitt costs $70. But you can buy a Frisbee for $3." Moreover, says Williams, it's a sport nobody outgrows. "I look forward to playing when I'm 65," he says with a grin. "There's never been a known fatality."