This is no way to start a discussion about manhood. We—Jack Johnson and me—are in a PT Cruiser. A sparkling, aquamarine, convertible PT Cruiser. We are driving through Burbank, California, on a cloudless 70-degree day in early March, and everyone on the road is wearing oversize shades. Still, even with the top up I can feel them staring as we wind westward toward the Ventura Freeway en route to the Los Angeles offices of Brushfire Records, Johnson's label. At a red light, two younger guys in a pickup give our ride the once-over, then grimace. If only they knew we were about to dive deep into a discussion of masculine energy.

It's Robert Bly's fault. I had been told before coming to Southern California that Johnson's new album, To the Sea, was heavily influenced by the poet and author, specifically Bly's 1990 bestseller, Iron John: A Book About Men. The book uses the Brothers Grimm fairy tale "Iron John" to explain the unfortunate state of the American man, who Bly says is indecisive, overly gentle, and sad. The "Iron John" tale, to massively simplify, is about a boy prince who frees a Wild Man (a.k.a. Iron John) caged in the royal castle and flees with him into the forest to be guided through a series of trials. As Bly sees it, modern men desperately need this kind of mentoring.

Johnson's keyboardist and longtime friend Zach Gill sent him the book last year, not long before Johnson's father died of cancer and his wife gave birth to their third child. "It was definitely good timing," he says.

No matter that Bly's heyday was 20 years ago. Back in the nineties, Iron John's mash-up of mythology, literature, and pop psychology helped inspire a lot of guys to reclaim their masculinity (say his fans) or simply gather in New Agey self-help groups to whine about their daddies (say critics). For several days before meeting Johnson, I dug into the book and wondered: Jack Johnson + Wild Man Power = what? He is, we have been told over the years, a very, very mellow dude. A 35-year-old Hawaiian surfer–cum–multiplatinum rock star most comfortable when he's barefoot on the beach, which is where you should be when you play his kick-back acoustic tunes. A writer of many, many love songs who takes his wife and kids on tour. A summer breeze incarnate. A soft man.

So far today, he has adhered to this image. This morning, when I walked into his band's rented rehearsal space in Burbank, the guys were drinking...tea. Now he's driving my rented Cruiser so I can take notes—so considerate. As we zip along the freeway, he confides that when he first started playing live shows, he would get so freaked out he'd almost faint. He's become more comfortable after having fans tell him "they danced their first dance to 'Better Together' or put on On & On while giving birth to their kid." It's hard to imagine Roger Daltrey taking strength from providing the soundtrack for someone's first dance.

And yet, something about Jack Johnson feels surprisingly—how to put it?—potent. For starters, he looks different. Wearing brown pants, with thick, bronzed arms popping out of a snug green T-shirt, he's surfer fit, as opposed to the doughy Johnson I first met in the middle of his 2005 summer tour. Tougher, too, and definitely more hirsute, with a beard and a thicket of sunbaked hair instead of the buzz cut he'd been giving himself for the past 20 years. Listening to the new album, it's clear that Iron John knocked a few things loose in Johnson's head. A number of songs on To the Sea take symbols directly from the fable, especially the title track, which has him singing from the Wild Man's point of view ("Unlock the pain, and I'll be here waiting"..."All your walls mean nothing to me. I know you'll come back, to set us free"). So, as we roll toward L.A., I ask Johnson: What's up with you and Iron John?

"I'm in the place where I've had a few kids and lost my own dad last summer," he answers. "It's this transitional period, where part of me is reaching in one direction and trying to hold on to the people I'm losing, and part of me is reaching the other way to hold on to these new kids coming into the world."

He squints at the traffic ahead. "I'm definitely starting to feel more like a father."