BACK IN TAHOE, Lisi seems worn down by the attention. "It stresses me out that some people are very angry. I'm not used to having enemies," he says between slices of homemade pizza. "There is a lot of press saying, ‘He is the next Einstein, he has solved everything!' It's probably bad for this theory, and for me personally, that it got this much attention."

Still, he admits to enjoying the encouraging e-mails. ("Nice work, man!" read one physics student's message. "I am trying to digest your theory right now... it's coming in focus slowly.") "Deep down, everybody wants to do what they want to be doing," Lisi says. "They just feel that they can't. So I think they find it kind of inspiring to see that it's possible. It just takes some sacrifices."

The next afternoon, Lisi suggests we go mountain biking on the Tahoe Rim Trail. Despite the late-fall chill, he shows up wearing tropical-print boardshorts. He rides with a kind of fearless joy, tearing down the trail at questionable speeds, whooping as he weaves between boulders, and soon disappearing ahead. When I finally catch up, Lisi has paused to check out a sweeping view of the valley. "Not bad, eh?" he says. "It's doing things like this that keep me from ever wanting to have a real job."

Right or wrong, Lisi offers a different approach to work and ambition—one that is potentially more valuable than an improbable, inscrutable theory of everything. "To my perception, Lisi hasn't advanced the story," says MIT physicist Frank Wilczek, a Nobel Prize winner. "That said, I admire people who think for themselves and dare to take on reality directly rather than writing footnotes to fashionable literature. So I hope he keeps trying and inspires others."

For now, at least, Lisi is no longer working alone. Other researchers have taken up parts of the E₈ theory to investigate, and Lisi says he'd consider a temporary academic post—if it were near decent snow or surf. "I've gotten e-mails asking, ‘Are you taking students?' " he says. "Well, come visit and I'll be happy to talk to you. But I'm not a degree-granting institution. And I don't want the surf breaks to get more crowded."

The danger of working out on the solitary edge of human thought, of course, is that the sharpest minds still need a check against self-delusion. Even the smoothest-seeming face can be plagued by hidden reefs. "It could be nature's big joke on me," Lisi says. "Sometimes we see patterns that aren't there. But it's certainly an adventure to think about. There aren't that many frontiers left in our world."