But Wood is not sitting in a lecture hall on the UC Berkeley campus, nor has he met Dreyfus. He is in the cab of his 18-wheel big rig, hauling dog food from Ohio to the West Coast or flat-screen TVs from Los Angeles to points east.The 61-year-old trucker from El Paso eavesdrops on the lectures by downloading them for free from Apple Inc.'s iTunes store, transferring them to his Hewlett-Packard digital media player, then piping them through his cabin's speakers. He hits pause as he approaches cities so he can focus more on traffic than on what Nietzsche meant when he said God was dead, then shifts his attention back to the classroom.
"I'm really in two places at once," he said. "The sound of chalk on the chalkboard makes it so real."
By making hundreds of lectures from elite academic institutions available online for free, Apple is reinvigorating the minds of people who have been estranged from the world of ideas.
For several years universities have posted recorded lectures on their internal websites, giving students a chance to brush up on their classes or catch ones they missed.
But 28 colleges and universities, including the Massachusetts Institute of Technology, Stanford and Yale, now post select courses without charge at iTunes.
The universities want to promote themselves to parents and prospective students, as well as strengthen ties with alumni. Some also see their mission as sharing the ivory tower's intellectual riches with the rest of the world.
"It was something we couldn't easily do before the digital age," UC Berkeley spokesman Dan Mogulof said.
These unofficial students, invisible to their instructors, won't earn degrees for listening. Some professors won't even respond to their correspondence. But they relish the explosion of free lectures.
Retirees in Long Beach and Weaverville, Calif., halibut fishermen in Alaska, data entry clerks in London, casting agents in New York -- all separated from the classroom by age, distance or circumstance -- are learning from some of the world's top scholars.
"Something revolutionary is happening," said UC Berkeley professor Richard Muller, whose Physics for Future Presidents class airs on iTunes. "A large number of people around the world want more education. They thirst for understanding and knowledge." One e-mail Muller received came with the subject line "Thank you from a grateful sailor in Iraq."
Apple began working with Duke University in late 2004 to broadcast classes from its website using iTunes software and has expanded the service to other schools. Separately, some universities started putting lectures on the iTunes store in the form of podcasts, which are free video or audio recordings that anyone can download to their computer or iPod.
The downloads have surged since May, when Apple began featuring lessons on the iTunes home page under the heading iTunes U. For example, the 86 courses UC Berkeley offers are now being downloaded 50,000 times a week, up from 15,000 before Apple's promotion.
Analysts say Apple foots the bill for storing and cataloging the recordings to create goodwill with universities, which are big buyers of its Macintosh computers. It has another motive: Podcasts drive demand for iPods.
For their part, universities are experimenting to see what works. Mogulof said UC Berkeley had no plans to charge for the podcasts but acknowledged that the benefits were unclear.
"We know there's oil under the ground," he said. "People are punching a lot of holes, and no one is sure what will come up as a big gusher."
The courses on iTunes U may not be the stuff of Casey Kasem's "American Top 40." But they are ranked nonetheless, and some become surprise download hits. One recent week, popular iTunes U podcasts included Modern Theoretical Physics from Stanford, Elementary Greek from Concordia Seminary in St. Louis and Intro to Biology from MIT.
It's a stretch to say that professors compete for iTunes popularity, but many are eager to know how many people tune in and see whether the university can benefit.
Dreyfus has cracked the top 20. He's the iTunes U equivalent of an indie rocker with a cult following.
Fans of his podcasts have trekked to his office in Moses Hall to meet him. Many have sent the university money, generally between $5 and $500, to show their appreciation for him and other podcasting professors, said Benjamin Hubbard, a co-manager of webcast .berkeley, which produces Berkeley's online courses and events.
One week last spring, before Apple started promoting the lectures on its home page, one of Dreyfus' philosophy and literature lectures -- he calls it "From Gods to God and Back" -- ranked 58th among podcasts on iTunes. It trailed programs from the BBC and Comedy Central but was downloaded more often than NPR's "This I Believe" and NBC's "Meet the Press."
To improve the sound quality of his lectures, Dreyfus agreed to teach in a room outfitted with a microphone and special recording device. But he is ambivalent about the benefits of broadcasting his philosophy class to the world. He said 25% of his enrolled students cut class.
One of the occasionally absent is Alexander Diaz, 18, a second-year philosophy major from Downey. He says he skips roughly every third class and listens, with his feet up, to the missed lectures through his iPod headphones on his back porch while he takes notes in the margins of Heidegger's "Being and Time."
"I'm pretty honored to take the class, but at the same time, when he does his lectures, it's not like I'm there with Dreyfus the man," Diaz said, referring to the impersonal feeling of sitting in a large lecture hall.
Dreyfus, who has taught at Berkeley since 1968, has long questioned the effectiveness of distance learning. In his 2001 book of essays, "On the Internet," he called the practice a "disembodied telepresence" and worried that remote students would take fewer risks than those sitting face-to-face with their instructors.
But Dreyfus says the chance to disseminate ideas softens his reservations. And the e-mails he receives from the listening audience -- "you podcast people," he calls them during class -- are touching.
Zachary Streitz soaks up the philosophy lectures as he baits hooks on a 58-foot fishing boat in the Gulf of Alaska, where he trawls for halibut and black cod. On shore, the 30-year-old fisherman loads up on course books.
"There are enough hours spent here that my hands are involved in the repetition that is my work, and my mind has more or less free rein to wander," he wrote to Dreyfus in June 2006. "If ever you are in need of any halibut, let me know."
Joe and Diane Mercier, who live outside Weaverville in Northern California's Trinity County, get their Dreyfus fix over morning coffee. They also listen to Muller's physics class from UC Berkeley and a Stanford course on geography and world cultures.
Joe, a 60-year-old evidence officer for the county Sheriff's Department, is annoyed by some of the routine instructions that begin and end classes as well as the sound of a student's phone ringing or a professor scolding someone for leaving early.
But he and his wife revel in the moment when Dreyfus dispenses with administrative work with his usual, "OK, here we go" and plunges into a philosophical discussion.
"We listen to relieve ourselves of mainstream television," Joe said.
He occasionally writes the papers that Dreyfus assigns but hasn't submitted any, unsure whether they would be read.
Arthur Marquis, 59, a former Justice Department attorney in Long Beach, told guests at his retirement party last year that he wanted to use his newly free time to see the world differently. They laughed.
Marquis, who graduated from UC Berkeley's law school decades ago, started taking French lessons at a local school. He found Dreyfus on iTunes and then bought an iPod so he could listen on his treadmill or outdoors.
"It's like electronic schizophrenia," he said. "I can hear voices in my head, and it's Dreyfus."
While other truck drivers talk to one another on their CB radios, Wood prefers to pass time on his weeks-long routes by sampling from an academic smorgasbord. He has listened to classes on astronomy from Ohio State University, geography from UC Berkeley and behavioral endocrinology from Johns Hopkins in Baltimore, which makes podcasts available through its website but not iTunes U.
"I'm a curious person," said Wood, who comes from a family of Pentecostal ministers and missionaries.
He attended the University of Alaska in the 1960s and remembered only one thing from his philosophy class: the name Kant (which belonged to the 18th century German thinker Immanuel Kant). He worked as a wood and stone turner until the dust started bothering him. In 2002, he became a truck driver.
This spring, he found the lectures on iTunes. "I felt like I discovered the Fountain of Youth," he said.
Wood doesn't listen to classes during his one week off the road each month, only when he's behind the wheel.
"For me, driving and listening are bound together like space and time," he said.
Sometimes, the classes that involve math or obscure concepts such as string theory lose him. But not Dreyfus' class, which he finds electrifying.
He remembers being somewhere in western Kansas in April when he heard Dreyfus' concluding lecture on existentialism, during which the professor asked students to vote, by raising their hands, for their favorite philosophies.
Dreyfus offered a thumbnail description of each: traditional Christianity, with God the creator and heaven; Kierkegaard's unconditional commitment to another person or cause; Dostoevski's unconditional commitment to all human beings; Nietzsche's belief in different identities, a life more like a series of short stories than a novel.
Wood, who long ago broke away from his family's religion, voted for Nietzsche silently.
"OK, that's it," Dreyfus said. "I have to stop and hand out the evaluations."
The class erupted in a sustained ovation, whooping and whistling.
The course had been recorded a year earlier. But Wood, separated by space and time, clapped and whooped too.
"Big trucks have enormous inertia. They practically drive themselves," he said. The machine, indifferent to his emotions, powered on, his body molded to the wheel, his mind having a great ride.